Preferably, the invention relates to transplant acceptance inducing cells (in the following also called TAIC) which are derived from human monocytes.

The invention moreover relates to the monoclonal antibody GM- 7, which specifically recognises transplant acceptance induc- ing cells according to the invention which are derived from man.

In addition, the invention relates to the use of the antibody GM-7 for detecting and/or selecting transplant acceptance in- ducing cells.

The term"transplantation"is used in the field of immunology for the transfer of cells, tissue or organs from one body to another. The need for transplantation arises from the finding that numerous diseases can be cured by transferring (trans- planting) healthy organs, tissue or cells from one individual who is healthy in this respect-the donor-to an individual suffering from the disease concerned-the recipient or host.

Depending on the relationship between the donor and the re- cipient, the following types of transplant can be distin- guished: 1. Autologous transplants: These are tissues or cells which are transplanted within one and the same individual from one area of the body to another.

2. Isologous transplants: This involves the transfer between genetically identical individuals. Examples of these are inbred strains of rats or mice. For man, isologous (synge- neic) transplants can be considered between genetically identical (monocygotic) twins.

3. Allogeneic transplants: This term designates transplants between genetically different members of the same species such as, for example, from one human individual to another or, in the case of experimental animals, from one inbred strain to another.

4. Xenogeneic transplants: This involves the transfer between different species such as, for example, the transfer of a monkey heart into a human being.

As a rule, autologous and isologous transplants cause no immu- nological problems in the sense of a rejection response. How- ever, this is not true in the case of allogeneic and xenolo- gous transplants. Such transplants are recognised as foreign by the recipient's immune system and rejected after a rela- tively short time. In the case of the allogeneic/xenologous rejection response, T-lymphocytes (hereinafter called T-cells) play a central part. These cells recognise the foreign cells by way of their major histocompatibility complexes (MHC). The foreign MHC-complex sensitises the antigen-reactive T-cells of

the recipient and, subsequently, the T-cells thus activated lead to the destruction of the donor cells or the donor tissue respectively. Cells with different MHC-complexes are also called"MHC-different".

Transplanting allogeneic or xenogeneic cells, tissues or or- gans necessarily leads to a situation where cells of two dif- ferent individuals, i. e. of MHC-different cells, are present in the blood of the recipient at the same time. This phenome- non is referred to as"chimerism". A distinction is made be- tween micro-chimerism and macro-chimerism. Micro-chimerism re- fers to a state in which cells derived from the donor, e. g. after a blood or bone marrow transfusion or after transplant- ing lymphocyte-rich organs such as the small intestine or the liver, remain persistent in the MHC-different host but are de- tectable only in a few isolated cases. The term macro- chimerism is used when more than 5% of the cells detected in the recipient originate from the donor, a distinction needing to be made in both cases between the blood and the organ chi- merism with the corresponding detection of donor cells in the recipient's blood or organs.

Chimerism can, to a certain extent, lead to tolerance vis-a- vis transplants. In the case of persons who, as a result of leukaemia or a lymphoma disease, for example, had to undergo an allogeneic bone marrow transplantation with a largely cor- responding MHC pattern between the donor and the recipient, a "donor chimerism"was thus observed after corresponding myelo- ablative conditioning (destruction of the individual's own bone marrow and the blood cells derived therefrom) and subse- quent stem cell transplantation. In the case of these pa- tients, more than 99% of the cells detectable in the blood originated from the donor's stem cells and this chimerism formed the basis for the tolerance vis-a-vis all organs trans-

planted from this donor. This observation was confirmed in a series of clinical examples of subsequent kidney, liver and <BR> <BR> lung segment donations [Dey B. , et al. ,"Outcomes of Recipi- ents of both bone marrow and solid organ transplants: A re- <BR> <BR> view. "Medicine (Baltimore) 77,355-369 (1989) ]. For a toler- ance induction to occur, it is not decisive in this connection that a complete donor chimerism-defined as the presence of more than 90% donor cells in the peripheral blood of an allo- geneic recipient-exists; instead, it has been found that a fraction of 5% donor cells-referred to as"mixed"chimerism - is sufficient to induce tolerance [compare survey by <BR> <BR> Acholonu I. N. and Ildstad S. T. ,"The role of bone marrow transplantation and tolerance: Organ-specific and cellular grafts", Curr. Opin. Organ. Transplant 4,189-196 (1999) ].

Although, basically, proof has thus been provided that the do- nor chimerism which accompanies a bone marrow transplantation (BMTx) induces tolerance, it has nevertheless not been possi- ble so far to carry out a successful allogeneic BMTx in the case of completely MHC-different donor and recipient constel- lations. This is due to the fact that the preconditioning re- quired for this, i. e. conditioning of the recipient (see above) holds three substantial types of risk for the recipi- ent. Firstly, the bone marrow toxicity of the chemotherapeutic agents used, which are administered together with or without additional radiation treatment, leads to a significant morbid- ity; secondly, there is the risk of the transplanted bone mar- row being rejected in spite of prior conditioning ; and, fi- nally, there is the risk of a graft versus host disease (GvHD) in the case of which the T-cells transferred into the host to- gether with the transplant turn against the host's organism [compare Wolff S. N. ,"Hematopoietic cell transplant from vol- unteer unrelated or partially matched related donors: Recent <BR> <BR> developments. "Curr. Opin. Organ. Transplant 5,372-381

(2000) ]. This disease occurs whenever the recipient's immune system has been weakened by the prior conditioning to such an extent that the T-cells transferred with the bone marrow are capable of causing a lethal rejection in the recipient.

To avoid the problems outlined above, efforts are under way at present to design the conditioning of the recipient to be as weak as possible. However, the greater the MHC difference be- tween the donor and the recipient, the stronger a conditioning treatment must be chosen in order to prevent the rejection of the transplanted bone marrow; this again leads to an increase of the risk of a graft versus host disease (GvHD).

So far, no detailed investigation has been carried out regard- ing the time for which the induced chimerism must remain de- tectable in the recipient's blood in order to guarantee a sta- ble tolerance situation for a donor organ. Reliable data from the mouse model, however, indicate that a macrochimerism de- tectable for two weeks is already sufficient for tolerance to arise [Weckerle, T. et al. "Allogeneic bone marrow transplan- tation with co-stimulatory blockade induces macro-chimerism and tolerance without cytoreductive host treatment. "Nat. Med.<BR> <P>6,464-469 (2000) ].

The need to develop alternatives to the immunosuppressants available at present to generate tolerance arises from the an- gle of two major points of view. On the one hand, the immuno- suppressants clinically available so far have not been capable of preventing chronic transplant rejection and, on the other hand, taking immunosuppressants permanently is accompanied by considerable side effects which make the patient prone to vi- ral, bacterial and mycotic infections and which generate sub- stantial risks through the formation of malignoma and diseases of the cardiovascular system, in particular by myocardial in-

farction and by cardial insufficiency [see Wheeler, D. C. and Steiger, J. "Evolution and Etiology of Cardiovascular Diseases in Renal Transplant Recipients"Transplantation 70,41-45 (2000)].

Munn et al. have described a macrophage-induced T-cell sup- pression, which is based on the selective elimination of Tryptophan and/or increase in one or more Tryptophan metabo- lites in the environment surrounding the cells [see Munn et al. "Inhibition of T Cell Proliferation by Macrophage Trypto-<BR> phan Catabolism"J. Exp. Med. 189,1363-1372 (1999) ]. Start- ing from this observation, the authors suggest to modify T- cell mediated immuno-reactions by the modification of the lo- cal extracellular tryptophan concentration, in particular by inhibiting or increasing the IDO-mediated Tryptophan- metabolism, see for instance the US-patens 6,482, 416 and 6,451, 840. Thus, this approach only provides a further anti- gen independent and unspecific immunosuppression directed against T-cells.

What is urgently needed, however, is a clinically applicable concept for inducing donor-specific tolerance, i. e. a concept according to which the host's immune response vis-a-vis the tissue antigens present on the organ transferred from the do- nor is specifically suppressed but in the case of which the host's immunocompetence is otherwise completely preserved.

By way of such a concept, a substantial reduction in the dis- crepancy between organ demand and organ supply would arise in the medium term since, in this way, far fewer organs would be lost as a result of acute and chronic rejection processes. The lack of suitable organs can be explained by way of statistics from the USA dating from February 2001: Type of transplant Number of patients on the waiting list Kidney 47,996 Liver 17, 151 Pancreas 1,060 Pancreatic islet cell 185 Kidney-pancreas 2,442 Intestine 151 Heart 4, 222 Heart-lung 210 Lung 3,721 Total number of patients 74,800 Table 1: Up-to-date data from"UNOS (United Nations Organ Share Registry) National Patient Waiting List for Organ Transplant (February 2001)" This explains the immense national and international efforts being made to develop concepts for inducing donor-specific tolerance.

It is consequently the problem underlying the invention to provide means for influencing the T-cells of the recipient or- ganism in such a way that they tolerate and/or accept the for- eign cells, tissues or organs concerned in the long term with- out rejection. The constitution of these means and their preparation or use should not cause any ethical and/or legal problems and it must be possible to prepare them rapidly for the intended therapeutic use in the quantities required for the purpose and at acceptable manufacturing costs.

For the solution of the problem, the transplant acceptance in- ducing cells of monocytic origin (TAIC) according to the in- vention from vertebrates, in particular form mammals, and more preferred from humans are provided. It has surprisingly been

found that monocytes from the blood of the donor (organ do- nor), modified according to the invention, are capable of pro- tecting the recipient organism, in the case of preoperative and/or postoperative administration, against its own body T- cells activated by the foreign MHC-complex thereby preventing the rejection of the transplant. When used as"cellular thera- peutic agents"for inducing transplant tolerance, the modified cells cause no or no noteworthy side effects in the sense of cellular rejection, induction of tumours, in particular of ma- lignant tumours and graft versus host disease in the patient concerned.

It has surprisingly been found that the process according to the invention leads to the in vitro modification of monocytes in such a way that cells are obtained which, after injection into a not immune suppressed allogeneic recipient, are capable of preventing the naturally occurring immune response against cells or tissue of the donor and which are thus capable of circulating in the peripheral blood for at least three weeks.

Following the administration of approximately 105 cells/kg body weight (BW), the resulting chimerism of GM-7 positive cells, see below, is in the region of 5-20%. This transient chimerism induces a) long-term acceptance for subsequent organ transplantations from the same donor, preferably within 10 days following the intravenous administration of the cells and b) long-term acceptance in combination with short-term immu- nosuppressive treatment when the cells are used subsequent to organ transplantation.

As shown in Example 10, the immunosuppressive effect of the cells of the invention are not associated with the macro-

phage-induced T-cell suppression by expression of the trypto- phan degrading enzyme Indolamine-2,3-Diogenase (IDO), as ob- <BR> <BR> served by Munn et al. , (see above). Rather, the TAIC of the invention induce a specific tolerance versus the donor in the recipient, by inactivating alloreactive T-cells on the one hand and by inducing the formation of regulatory T-cells in the recipient on the other hand, see Examples 12 and 13.

Macrophages derived from monocytes, which inhibit the prolif- eration of T-cells by an IDO-mediated elimination of Trypto- phan in the environment surrounding the cells, are therefore not included in the invention.

Description of the Figures Figure 1 : Flow cytometric determination of the binding ca- pacity of GM-7 to original monocytic cells before (graph on the left hand side) and after (graph on the right hand side) modification of the cells according to the invention. The x axis indicates the number of bound cells.

Figure 2A: Kaplan-Meier survival curves of heart transplants following heterotopic heart transplantation with and without preoperative administration of donor- derived TAIC in the rat model (n = 10 animals per group).

Figure 2B: Histological preparation of an LEW allogeneic transplant on POD (postoperative day) 150 follow- ing heterotopic transplantation into the abdomen of a DA recipient rat that had been pre-treated

on day-7 with 106 LEW-derived TAIC. Magnification factor: 40.

Figure 2C: Histological preparation from the thymus of a DA rat pre-treated with 106 LEW-derived TAIC follow- ing labelling of the preparation with the mono- clonal antibody I1. 69 specific for LEW-MHC class I. Magnification factor: 40.

Figure 2D: Flow cytometric detection of donor-derived cells in four DA recipient rats not subjected to immu- nosuppression following the injection of LEW- derived TAIC (rats 1-3: 106 cells/kg x BW; rat 4: 104 cells/kg x BW).

Figure 3: Kaplan-Meier survival curves of heart transplants following heterotopic heart transplantation with and without postoperative administration of do- nor-derived TAIC in combination with an initial administration of 4 cycles of Cyclosporin A (CSA; 5 mg/kg x BW) in the rat model (n = 6-10 ani- mals per group).

Figure 4A-C: Kaplan-Meier survival curve of heart (A), liver (B) and kidney (C) transplants following hetero- topic (A and C) or orthotopic (B) transplantation respectively with and without preoperative ad- ministration of donor-derived TAIC (n = 6 animals per group).

Figure 4D-F: Histological preparations of DA transplants of the kidney (D), the liver (E) and the skin (F) following heterotopic transplantation into a LEW recipient rat.

Figure 5A: Kaplan-Meier survival curves of heart transplants following heterotopic heart transplantations of different combinations of inbred strains with and without postoperative administration of donor- derived TAIC in combination with an initial ad- ministration of 4 cycles of CSA (5mg/kg x BW) in the rat model (n = 6 animals per group).

Figure 5B: Kaplan-Meier survival curves of heart transplants following heterotopic heart transplantations 7 days after the administration of differently treated blood monocytes from LEW donor animals (n = 6 animals per group).

Figure 6A: Kaplan-Meier survival curves of lung transplants following orthotopic left sided lung trans- plantations in pigs ("outbred minipigs") using a triple immunosuppression of CSA, Azathioprin (AZA) and steroids (STE). (n = 4 animals per group).

Figure 6B: X-ray picture of the thorax (posterior-anterior technique) of two single-side left lung trans- planted pigs ("outbred minipigs") on POD (postop- erative day) 41 and 55. The triple immunosuppres- sion of CSA, AZA and steroids was discontinued on day 28 after transplantation.

Figure 7: Mixed lymphocytes culture of CD14+ monocytes from an individual B (GM-7- : grey column ; GM-7+ : black column), responder cells from an MHC-discordant donor A and irradiated cells from a donor B to

compare the suppressor activity of CD14+/GM-7+ and CD14+/GM-7-cells.

Figure 8: Mixed lymphocyte culture of PHA-stimulated lym- phocytes (PhaLy) and TAIC ("Mo+Ly"or"Mo"), preincubated in two experiments with an inhibi- tor (1-MT) of indolamine-2,3-dioxygenase (IDO) for determining the influence of 1-MT on the suppressor activity of the TAIC.

Figure 9: Flow cytometric determination of the amount of CD14+-monocytes and of CD2+-lymphocytes in the monocyte fraction as well as the amount of the CD-14+/CD3+-cells effective as TAIC, for deter- mining the influence of purifying the cells for enriching monocytes at the beginning of the cul- ture on the formation of immunosuppressive CD14+/CD3+-cells.

Figure 10: Flow cytometric determination of GM-7-expression in the blood of patients postoperatively prior (left Figure) and after (right Figure) injection of TAIC, for determining the influence of TAIC on the in vivo-GM-7-expression in blood cells.

Summary of the invention The main steps of the process according to the invention for the preparation of TAIC of monocytic origin comprise: (a) Isolating monocytes from blood, preferably from human blood;

(b) Propagating the monocytes in a suitable culture medium which contains the macrophage colony stimulating fac- tor (hereinafter referred to as M-CSF) as growth pro- moting agent; (c) Stimulating the monocytes with y-interferon (hereinaf- ter called y-IFN) ; and (d) Obtaining the transplant acceptance inducing cells formed in stage c) by separating the cells from the culture medium.

According to the invention, it has been shown that the stimu- lation with y-IFN represents a decisive step in the prepara- tion of TAIC (see Example 7).

With respect to the present invention the term"TAIC" (trans- plant acceptance inducing cells of monocytic origin) desig- nates the cell population, which is obtained from step (d) of the process described above. This cell population comprises next to the cells derived from monocytes, which are effective according to the invention, also lymphocytes, see Example 11, as well as optionally further cells derived from the buffy- coat, as for instance granulocytes. The amount of cells de- rived from monocytes within the TAIC-population is preferably 50 to 90 %, more preferably 60 to 70 %, referring to the to- tal cell number.

With respect to the present invention the term"total cell number"refers to the amount of vital cells in the cell popu- lation under consideration. This amount can be determined by the"trypan blue dye exclusion technique", since this dye al- lows to distinguish vital cells from non-vital cells by opti- cal means.

The TAIC according to the invention may usually be used in a quantity of 104-106 cells per kilogram body weight, preferably 105 cells per kilogram body weight, to induce transplant accep- tance. TAIC administration may be carried out repeatedly, in the case of a large MHC difference preferably three times at intervals of approximately 10 days where the administration of the cells may take place prior to or after transplantation (see below). The total number of cells necessary for this pur- pose can be provided within 6 to 8 days after the blood was taken.

The cells according to the invention (TAIC) have proved to be risk-free regarding the formation of malignoma, both in the animal test and in culture; this is a result which could not have been expected in any other way because of the nature of the original monocytic cell from which the cells according to the invention are derived.

As explained below, further sub-populations of cells having optimized effectivity according to the invention, can be iso- lated from the fraction of cells present in TAIC, which are derived from monocytes.

Following in vitro cultivation and stimulation of the original cells (monocytes) with y-interferon TAIC are formed, which comprise a sub-population of cells, see Example 9, which binds the monoclonal antibody GM-7, which is expressed by the hy- bridoma cell line DSM ACC2542. The monoclonal antibody GM-7 is an antibody of the immunoglobulin isotype IgG2a, the light chain of which exhibits the kappa-isotype. The characteristic property of this antibody is its stringent capacity to bind to the monocytes modified by the culture conditions according to the invention since original monocytic cells are not recog-

nised, i. e. binding of the antibody to the original cells does not take place, (see Example 9). In addition, it was demon- strated with 20 volunteers that GM-7 does not bind to human cells in the peripheral blood, see Figure 10.

The antibody was prepared by immunising mice with TAIC derived from human monocytes using methods known to the person skilled <BR> <BR> in the art (Davis, W. C. "Methods in Molecular Biology: Mono- clonal Antibody Protocols", New York: Humana Press Inc.

Totowa, 1995). A hybridoma cell line was then produced by fu- sion of a B cell generating the antibody and a myeloma cell from the mouse. Methods used for the preparation of such cell lines are known in the state of the art (Davis, W. C."Methods in Molecular Biology: Monoclonal Antibody Protocols", New York: Humana Press Inc. Totowa, 1995 ; Kohler, G. , Milstein, C.

"Continuous cultures of fused cells secreting antibody of pre- defined specificity", Nature 256,495-497 (1975) ). The hybrid- oma cell line producing the antibody GM-7 was deposited ac- cording to the rules of the Budapest Convention at DSMZ (Deut- sche Sammlung von Mikroorganismen und Zellkultur GmbH, Braunschweig, Germany) under the accession no. DSM ACC2542.

Figure 1 shows the binding capacity, determined by flow cy- tometry, of GM-7 to monocytic cells after in vitro modifica- tion according to the invention. It can be seen that the CD14- positive monocytes obtained directly from buffy-coat do not bind the antibody GM-7 (the cloud shaded grey is congruent with the non-shaded antibody control). In contrast, following cultivation in the presence of M-CSF and stimulation with y- IFN, part of the monocytes express an antigen which is recog- nised by the monoclonal antibody GM-7. The monoclonal antibody GM-7 was characterised as isotype K-IgG2a. The process accord- ing to the invention consequently leads to a change in the

phenotypic pattern of the antigen expression on the cell mem- brane of the modified monocytes (Figure 1).

The monoclonal antibody GM-7 binds specifically to that cell population which, among those cells produced by the process according to the invention, induce the most effective trans- plant acceptance (see Figure 9).

Therefore, a preferred embodiment of the invention relates to such TAIC, which are capable of binding the antibody GM-7.

These cells are subsequently designated as TAICGM7.

The antibody GM-7 according to the invention therefore repre- sents an extraordinarily effective and easy to handle agent for selecting and purifying the cells inducing transplant ac- ceptance (TAIC). By means of the antibody, it is possible ac- cording to the invention to generate a homogeneous and highly effective TAIC population.

According to a preferred embodiment of the invention, the transplant acceptance inducing cells formed in step c) of the above described process of the invention, which express the antigen binding to the antibody GM-7, may either be selected directly from the culture medium after step c), or they may be selected from the cell population obtained after separating the cells from the culture medium according to step d) of the above-mentioned process of the invention by binding to the an- tibody GM-7 produced by the hybridoma cell line DSM ACC2542.

To select the TAIC according to the invention, the antibody is contacted with the sample under conditions which permit bind- ing of the antibody to the transplant acceptance inducing cells present in the sample. The reaction complexes resulting from the binding reaction are subsequently separated from the

- sample. For this purpose, the antibody can be immobilised on a carrier material before contact with the sample ; for example, it can be bound to a matrix suitable for chromatographic pur- poses or to so-called"magnetic beads". This procedure allows to select and concentrate transplant acceptance inducing cells from large volumes of sample.

To obtain the transplant acceptance inducing cells, the bond between the antibody and the transplant acceptance inducing cells is separated after the isolation of the reaction complex from the sample. This can be effected by methods known in the state of the art such as e. g. by competitive displacement or by washing with salt solutions. Corresponding methods are for instance described by Utz U. et al. ("Analysis of the T-cell Receptor repertoire of human T-cell leukemia virus type-1 (HTLV-1) Tax-specific CD8+ Cytotoxic T Lymphocytes from pa- tients with HTLV-1 associated disease: Evidence for the oli- goclonal expansion"J. of Virology Feb. 1996,843-851).

Moreover, the monoclonal antibody GM-7 permits the qualitative and quantitative detection of the transplant acceptance induc- ing cells of monocytic origin according to the invention in blood and/or tissue samples of the patient in vitro. This pa- tient may, for example, be the recipient of an organ yet to be transplanted or already transplanted. The formation of reac- tion complexes in the sample which indicate the presence and, if applicable, the quantity of the transplant acceptance in- ducing cells is detected by known methods.

To detect the reaction complexes, it is possible in this case to couple ("label") the antibody GM-7, for example, directly with a detectable molecule which is e. g. covalently bound to the antibody. Suitable detectable molecules are described in large numbers in the field of molecular diagnostics and in-

clude, among others, fluorescent dyes such as fluorescein iso- thiocyanate or tetramethyl rhodamine-5-isothiocyanate, lumi- nescent dyes, radioactively labelled molecules and enzymes such as peroxidases (compare Lottspeich, F. , Zorbas, H."Bio- analytik", Spektrum Akademischer Verlag GmbH, Heidelberg- Berlin, 1998).

The detection of the antibody takes place dependent of the molecule selected for labelling of the former. In connection with the present invention, the antibody GM-7 was coupled with the fluorescent molecule fluorescein isothiocyanate (FITC) so that the detection of the antibody could be carried out by means of flow cytometry and/or fluorescence microscopy. Meth- ods for labelling antibodies with FITC are known to the person skilled in the art who operates in the field.

Alternatively, the reaction complex can also be detected in a two-stage process using secondary antibodies. In this connec- tion, the unlabelled antibody GM-7 can be detected in the re- action complex with a further labelled antibody (compare Lott- speich, F. , Zorbas, H. "Bioanalytik", Spektrum Akademischer Verlag GmbH, Heidelberg-Berlin, 1998). This two-stage method of detection is considerably more sensitive than the direct detection of binding of the antibody according to the inven- tion since several labelled secondary antibodies can bind to one GM-7 antibody (signal amplification).

The antibody GM-7 consequently allows the detection of TAIC in the peripheral blood of the patient treated with TAIC, for ex- ample in the form of"monitoring", during which the number of cells in the peripheral blood is determined at specific time intervals. According to the invention, it has been found that the presence of TAIC prepared from monocytes of the donor cor- relates, in the animal test in the peripheral blood of the

transplant recipient, with the tolerance of the transplanted organ. This finding consequently permits the clinician to wean off or to reduce the dosage of the immuno-suppressants that are optionally administered stepwise. Previously, it had not been possible from the clinical point of view to provide accu- rate evidence as to whether the immune system of a patient ex- hibited tolerance at a given point in time following trans- plantation.

As is obvious to the person skilled in the art, it is possible to prepare monoclonal antibodies against TAIC from monocytes also of non-human vertebrates, in particular from monocytes of primates and pigs modified according to the invention. In this respect, the immunisation of the corresponding host animals and the generation of the corresponding hybridoma cell line are carried out as described above for the TAIC of human ori- gin. The generation of effective TAIC populations from other species provides an important contribution in the field of xe- nogeneic transplantation medicine.

A particularly preferred embodiment of the invention relates to a sub-population of the TAIC of the invention, which co- express the antigens CD3 and CD14 on their cell surface.

These cells are subsequently indicated as TAICCD3+/cDi4+. Such cells have to date not been reported in the state of the art.

Monocytes and known cells derived from monocytes do carry the surface marker CD14, however, they do not additionally carry the surface marker CD3 at the same time.

TAIC which co-express the surface antigens CD3 and CD14 may either be directly selected from the transplant acceptance in- ducing cells formed in step c) of the above described process of the invention, or they may be selected from the cell popu- lation obtained after separating the cells from the culture

medium according to step d) of the above-mentioned process of the invention, or they may alternatively be selected from the TAICGM7 population.

Further, it has been shown according to the invention that the TAICCD3+/CD14+ express the genes Foxp3, CTLA4 and Integrin aEp7 strongly (see Example 12). In contrast, these genes are not or only to a small extent expressed by the original mono- cytes. The upregulation of the expression of the genes Foxp3, CTLA4 and Integrin (XEP7 is therefore a characteristic of TAICcD3+/cDl4+-cells.

As discussed in Example 12, the expression of the markers FoxP3, CTLA4 and Integrin axe 7 was previously only described for regulatory T-lymphocytes. T-lymphocytes, which co-express the surface antigens CD4 and CD25 are a sub-population of regulatory T-lymphocytes, which are also indicated as"sup- pressor cells". It is their function to suppress the immune response of the body. In particular, Foxp3 is seen as a spe- cific transcription factor, which serves as a control gene for the development of regulatory T-cells, and which is spe- cifically expressed by these cells. According to the inven- tion, it is preferred that the TAICcD3+/cDi4+-cells express at least 1 x 10-9, more preferably at least 5 x 10-9, and in par- ticularly preferred manner at least 1 x 10-8 g Foxp3-RNA per pg total RNA.

CTLA4 is similarly viewed as a marker for the detection of the regulatory function of T-lymphocytes, in particular of CD4/CD25 positive T-lymphocytes (see the literature cited in Example 12). According to the invention, the TAICCD3+/CD14+- cells should preferably express at least 5 x 10-7, more pref-

erably at least 3 x 10-6 and in a particularly preferred man- ner at least 5 x 10-6 pg CTLA4-RNA per ig total RNA.

Integrin aEß7, which recognizes epithelial Cadherin was re- cently described by Lehmann et al. in PNAS 99, pages 13031- 13036 (2002) as a new marker for a sub-population of highly potent regulatory T-lymphocytes, which interact with the epithelial environment. The expression of the Integrin aEa7- RNA should according to the invention amount in TAICcD3+/cDi4+- cells to preferably at least 1 x 10-12, more preferably to at least 1 x 10-11, and in a particularly preferred manner to at least 1 x 10-1°, and most preferably to at least 1 x 10-9 pg per 1 pg total RNA.

As shown in the Table in Example 12, the direct co-culturing of the TAIC of the invention with lymphocytes leads to a sig- nificant increase in the number of regulatory T-lymphocytes, in particular of CD4/CD25 double-positive cells in the lym- phocyte population with strongly up-regulated expression of the genes Foxp3, CTLA4 and Integrin CAP7. The Example further demonstrates that this effect is not observed if TAIC are in- directly co-cultured with lymphocytes.

These results indicate that stimulation of the formation and/or propagation of regulatory T-lymphocytes by TAIC is in- volved in the induction of transplant acceptance by the TAIC of the invention.

Example 13 confirms this hypothesis. In this Example, lympho- cytes from the recipient animals of Examples 3,4, 5,6 and 7 were incubated with TAIC from the respective donor animals in vitro. For the induction of tolerance, TAIC pre-incubated with the lymphocytes from the recipients were injected to the

animals instead of TAIC. Donor specific tolerance could be induced also in this manner, while animals, to which recipi- ent lymphocytes not co-cultivated with donor derived TAIC were administered, did not develop tolerance.

The TAIC of the invention can be used as such as pharmaceuti- cal preparation. The cells obtained from step d) of the method of the invention as described above can be used di- rectly. About 10-50 % of the total cells of the populations so obtained is formed by lymphocytes and granulocytes, which stem from the initial monocyte isolate (buffy-coat). These cells support the formation of the TAIC of the invention de- rived from the monocytes in the culturing step (see Example 11); they do not interfere with the tolerance induction if the TAIC of the invention are used as a pharmaceutical prepa- ration.

However, according to further preferred embodiments of the invention, the sub-populations TAICGM7 and/or TAICcD3+/cDi4+ may be isolated from the totality of the TAIC population obtained from process of the invention (see above) and may be used for tolerance induction.

In culture media (see Example 2), the TAIC or the TAICGM7 and/or TAICCD3+/CD14+ may be kept for at least 48 hours without their tolerance inducing effect becoming lost.

For use as pharmaceutical preparation, the TAIC or the sub- populations TAICGM-7 and/or TAICCD3+/cDi4+ suspended in e. g. human AB serum (universally suitable for use) can be administered intravenously as short transfusion. For the induction of transplant acceptance in the case of allogeneic transplanta- tion, the TAIC generated from the monocytes of the donor or the sub-populations TAICGM7 and/or TAICCD3+/cDi4+ can be injected

into the MHC-different recipient either pre-operatively or postoperatively. In the case of preoperative administration, the TAIC should be injected once to three times approximately 1 week before the operation. In the case of postoperative ad- ministration, the period between the operation and the single administration of the cells should not be longer than 7 days.

The TAIC according to the invention or the sub-populations TAICGM7 and/or TAICCD3+/cDi4+ are then capable of repelling the T- cell response of the recipient's immune system against the transplant and to persist in the recipient blood for a suffi- ciently long period of time to guarantee long-term transplant acceptance.

Preoperative intravenous injection can be considered in con- nection with donations from living individuals; however, if a corpse donation (blood and organ from a dead body) is at is- sue, postoperative administration of the TAIC according to the invention or the sub-populations TAICGM7 and/or TAICCD3+/cDi4+ may be preferred. In the case of a corpse donation, the body of the donor is flushed with a perfusion medium by canalisation of the principal artery for purposes of organ preservation. In this case, the venous blood is normally sucked out via the vena cava and discarded. To obtain the TAIC to be used accord- ing to the invention, the venous blood can be collected and processed as described in Example 1. In the alternative, in the case of corpse donation, TAIC may also be obtained from cells (lymphocytes and monocytes) from the donor spleen.

In the case of postoperative application of the TAIC according to the invention in connection with corpse donation, the in- terval between the transplantation and the application of the cells can be overcome by combination with immuno-suppressants, in order to prevent an acute rejection of the organ in the in- terval between the transplantation and the provision of the

TAIC obtained from the donor blood. In this connection, thera- peutic combinations with conventional immuno-suppressants such as, for example, calcineurin inhibitors such as cyclosporin A (CSA) or tacrolimus or with azathioprine (AZA), mycophenolate mofetil, rapamycin, monoclonal antibodies (ATG, ALG, but nei- ther with Dicliziumab or Basiliximab) or steroids (STE) can be considered. The presence of immuno-suppressants (except for known IL-2-receptor-a monoclonal antibodies such as Dicliziu- mab and Basiliximab) in the recipient blood has no negative effect on the effectiveness of the immuno-suppressants, on the one hand, or the TAIC, on the other hand.

In this sense, the cells of monocytic origin which have been modified according to the invention can be used as"vehicle for tolerance transfer"for any cellular transplant (such as islet cells, hepatocytes, adult stem cells and for any other programmed cell type or tissue type) and organ (such as e. g. kidney, liver, heart) insofar as they are genetically identi- cal to the cells to be transplanted (organs), i. e. they must originate from the donor him/herself or from identical twins thereof. The TAIC fulfil their protective function by allowing the transplanted cells/organs to become adherent in the new environment, thus saving the recipient from suffering the side effects of a longterm immunosuppressive therapy.

Detailed description of the invention The starting cells for the process according to the invention are blood monocytes. These are preferably monocytes from human blood. For purposes of inducing transplant acceptance, the cells must originate from the donor of the transplant (or his/her identical twin). In the case of xenogeneic trans- plantations of e. g. monkey or pig organs into man, the TAIC

according to the invention must consequently be derived from the monocytes of the donor animal concerned.

To obtain the monocytes, the blood can first be separated, af- ter the usual treatment with an anticoagulant, into plasma and into white and red blood cells using methods known in the art, preferably by centrifugation. After centrifugation, the plasma will be present in the supernatant; below it, there is a layer which contains the white blood cells in their entirety. This layer is also referred to as buffy-coat. Below this is the phase containing the red blood cells (hematocrit).

In connection with the process according to the invention, the buffy-coat layer is first isolated and separated to obtain the monocytes e. g. by centrifuging according to known methods. Ac- cording to a preferred process embodiment, the buffy-coat layer is applied onto a lymphocyte separation medium (Ficoll- Hypaque) and centrifuged (see Example 1). Example 1 describes the preferred embodiment of the invention, wherein the eryth- rocytes and dead cells still contained in the buffy-coat are separated by centrifuging, and the white blood cells includ- ing the monocytes are present as an isolate on the separation medium. Thereafter, the white phase of monocytes may be care- fully pipetted off, and, for enrichment of the monocytes within the isolate, are repeatedly centrifuged and washed. In the course of this process, the monocytes will assemble at the bottom of the centrifuge vessel together with a part of the lymphocytes.

According to a particularly preferred embodiment of the method of the invention, the conditions for obtaining the monocyte containing isolate are controlled such that the iso- late contains about 10-50 % lymphocytes next to the mono- cytes, by reference to the total number of cells. Preferably,

the isolate contains about 50-90 %, in a particularly pre- ferred manner 60-70 % monocytes and about 10-50 %, in a particularly preferred manner 20-50 % lymphocytes, each by reference to the total cell count, wherein the difference will optionally be provided by granolocytes.

As shown in Example 11, the presence of lymphocytes in a mag- nitude of 20-30 %, referred to the total cell count, during the culturing of the original monocytes with MCSF and y- interferon will lead to the generation of a significantly higher amount of CD3/CD14-double positive TAIC, as will be the case if only a few lymphocytes (about 5 %) are present.

To prepare a sufficient quantity of TAIC, it is first neces- sary to allow propagation of the monocytes. For this purpose, known growth media suitable for monocytes can be used; how- ever, the medium must contain the growth factor M-CSF (macro- phage-colony-stimulating-factor). M-CSF (also-called CSF-1) is produced by monocytes, fibroblasts, lymphocytes and endothe- lial cells. The concentration of M-CSF in the culture medium may preferably amount from 2 to 20 ug/1 medium, more prefera- bly 4 to 6 ug/1 and in particularly preferred manner 5 pg/l.

Subsequently or simultaneously, the cells must be stimulated with y-IFN, i. e. cultured in the presence of y-IFN. The stimu- lation of the monocytes with y-IFN takes place after an ini- tial propagation phase lasting 3 to 6 days in the culture me- dium containing the growth factor. Preferably on day 4 after the beginning of cultivation, y-IFN stimulation is carried out and this stimulation is extended over a period of preferably 24 to 72 hours, more preferably 48 hours under incubator con- ditions i. e. at 37°C and in a 5% C02 atmosphere.

The concentration of y-IFN in the medium may be 0.1 to 20 ng/ml, preferably 1 to 10 ng/ml and particularly preferably 5 ng/ml.

The stimulation with y-IFN may begin simultaneously with the propagation of the monocytes in the medium containing the growth factor. However, stimulation after a 3 to 6 day long initial propagation phase, as indicated above, is preferred.

The propagation of the cells and stimulation with y-IFN should, overall, preferably not take more than 8 days. In any case, treatment with y-IFN should be carried out such that af- ter the propagation phase it lasts for at least 24 hours, at maximum 72 hours, preferably 48 hours. The period for propaga- tion and stimulation of the cells should consequently last for a total of preferably 4 to 8 days.

According to a preferred embodiment of the invention, the propagation and stimulation with y-interferon is carried out as indicated in Example 2 in such a way that the monocytes are first propagated in a culture medium containing the growth factor and that y-IFN is added to the culture medium after 3 to 6 days in such an amount that a concentration of 0.1 to 20 ng/ml, preferably 1 to 10 ng/ml and particularly preferably 5 ng/ml is obtained in the medium.

Preferably, the process according to the invention is carried out in culture vessels the surface of which has previously been coated with fetal calf serum (FCS) or alternatively with human AB serum (see Example 2). Coating with FCS can take place by covering the surface of the culture vessels with FCS before use and, following a period of interaction of a few hours, in particular 4 to 72 hours, preferably 12-48 hours and in particular 24 hours, removing the FCS not adhering to the surface in a suitable manner.

During the culturing step the cells will settle at the bottom of the culturing vessel after about 24 hours. Due to their adhesive properties the monocytes and the TAIC, derived from the monocytes during the process, will then adhere to the bottom of the respective culture vessel. If, as described in Example 2, the culture medium is changed during cultivation, the supernatant is initially carefully removed, for instance by pipetting off or decanting, and subsequently fresh culture medium is filled in. Preferably however, the cells adhering to the bottom are not or only carefully washed, so that any lymphocytes present are not removed.

Removing the adhering cells can take place mechanically, e. g. by means of a fine cell scraper or spatula.

According to a preferred embodiment of the process according to the invention, however, the complete removal of the cell takes place by treatment with a suitable enzyme, e. g. with trypsin (see Example 2). The trypsin solution (0.1 to 0.025 g/1, preferably 0,05 g/1) can be allowed to act onto the cells for 2 to 10 minutes at 35°C to 39°C, preferably at 37°C, in the presence of 5% CO2.

The enzyme activity is then blocked in the usual manner and the now freely floating TAIC can be obtained in the usual way by centrifuging. They are then available for immediate use, optionally in suspension in a suitable medium, e. g. in PBS.

However, they can also be kept for several days, in particular for approximately 2 to 3 days, in a nutrient medium (see Exam- ple 2); wherein this preservation medium should contain nei- ther the growth factor nor Y-IFN. The cells can be kept in such a nutrient medium as TAIC for at least 48 hours.

For storage over longer periods, the cells can be deep frozen.

Protocols for deep freezing of living cells are known in the state of the art, compare Griffith M. et al. , ("Epithelial Cell Culture, Cornea", in Methods of tissue engineering, Atala A. and Lanza R. P. , Academic Press 2002, chapter 4, pages 131- 140). A preferred suspension medium for deep freezing of the cells according to the invention is FCS containing DMSO.

According to one embodiment of the invention the cell suspen- sion containing transplant acceptance inducing cells obtained from steps c) or d) may be further purified with respect to those cells, which bind the antibody GM-7, so as to obtain a sub-population TAICGM7. Methods for such purification are de- scribed above in detail.

According to a further, preferred embodiment of the invention such cells are selected from the TAIC population, which co- express the antigens CD3 and CD14 on their cell surfaces.

Methods for selecting such cells are known in the art. Exam- ples for such methods are the"Fluorescent-Activating Cell Sorting" (FACS), the"Immuno Magnetic Bead Sorting"and the "Magnetic Activated Cell Sorting" (MACS), or the so-called "Rosetting Method" [see Gmelig-Meyling F. et al."Simplified procedure for the separation of human T-and non-T-cells", Vox Sang. 33,5-8 (1977) ].

The selection of the TAIC sub-population TAICCD3+/cDi4+ can take place directly from the TAIC population obtained from steps c) or d) of the above-described process of the invention, or from the TAICGM7-sub-population. The latter way to proceed means that a stepwise enrichment of TAICCD3+/cDi4+ will take place.

In a preferred embodiment of the invention the TAIC according to the invention are used per se for the production of a phar-

maceutical composition for the in vivo suppression of trans- plant rejection.

Such pharmaceutical preparation may contain vital TAIC accord- ing to the invention, which are obtained from step d) of the process of the invention, suspended in a pharmaceutically ac- ceptable carrier preferably in a quantity of about 1 x 105 to 1 x 107 cells/ml and more preferably of about 1 x 106 cells/ml of the preparation.

In a further preferred embodiment of the invention the cells of the TAICGM7 sub-population according to the invention are used per se for the production of a pharmaceutical composition for the in vivo suppression of transplant rejection.

Such pharmaceutical preparation may contain vital TAICGM7 cells according to the invention, which bind to the antibody GM-7, suspended in a pharmacologically acceptable liquid carrier, preferably in a quantity of about 1 x 10"to 1 x 108 cells/ml and more preferably of about 1 x 106 cells/ml of the prepara- tion.

In a particularly preferred embodiment of the invention the cells of the TAICCD3+/cDi4+ sub-population according to the inven- tion are used per se for the production of a pharmaceutical composition for the in vivo suppression of transplant rejec- tion.

Such pharmaceutical preparation may contain vital TAICcD3+/cDi4+ cells according to the invention, which co-express the anti- gens CD3 and CD14, in a quantity of preferably about 5 x 105 to 5 x 107 cells/ml and more preferably of about 5 x 106 cells/ml of the preparation.

The above described pharmaceutical preparations may contain the cells according to the invention suspended in a physio- logically well-tolerated medium. Suitable media are for exam- ple Ringer solution, physiological saline or 5 to 20 % human albumin solution and the like.

Cell preparations according to the invention may contain vital TAIC, which are obtained from step d) of the process of the invention. Alternatively, the preparations may contain cells belonging to the sub-populations of TAICGM7 cells, which bind to the antibody GM-7, or of TAICCD3+/cDi4+ cells, which co-express the antigens CD3 and CD14 on their cell surface. The prepara- tions may contain the respective cells in a quantity of pref- erably at least 1 x 105, more preferably at least 5 x 105 and most preferably at least 1 x 106 cells per ml suspended in a liquid carrier medium. The medium may be a cell culture or transport medium well-tolerated by cells, such as 5 to 20% hu- man albumin solution. Alternatively, the cells within the preparation may be deep-frozen and contained in a suitable storage medium, such as e. g. RPMI with 50% human albumin solu- tion and 10% DMSO.

Finally, the invention also relates to a method wherein the transplant-acceptance inducing cells of the invention (TAIC, TAICGM7 or TAICCD3+/cDi4+) are used for generating or expanding regulatory T-lymphocytes in vitro. As shown in Example 12, the direct in vitro cocultivation of TAIC with lymphocytes leads to a significant proliferation of regulatory T-lymphocytes, in particular of CD4+/CD25+ lymphocytes, see Wood and Sakaguchi: "Regulatory Cells in Transplantation Tolerance", Nature Review Immunology 3,199-210 (2003). It is therefore possible to gen- erate and/or expand regulatory T-lymphocytes in particular

CD4+/CD25+ lymphocytes by directly coculturing TAIC with lym- phocytes as described in Example 12.

Direct in vitro culturing means according to the invention that TAIC and lymphocytes are cocultured in direct physical contact within the same medium, as a. o. exemplified in Example 12.

In this method the medium preferably contains the respective cells i. e. TAIC and lymphocytes in about equal cell numbers and each in a quantity of preferably at least 1 x 105, more preferably at least 5 x 105 and most preferably at least 1 x 106 cells per ml suspended in a liquid carrier medium; the me- dium may be a cell culture or transport medium well-tolerated by cells, such as 5-20% human albumin solution. The co- cultivation preferably should take place under physiological conditions at about 37°C, e. g. in an incubator, for preferably about 3 to 5, more preferably 4 days.

As shown in Example 13, transplant acceptance can not only be induced by administering TAIC generated from donor monocytes to the recipient, but also by readministering recipient lym- phocytes to the recipient, which have previously been directly cocultured in vitro with TAIC prepared from donor monocytes as described above.

According to a further embodiment of the invention regulatory T-lymphocytes can therefore be prepared in vitro from lympho- cytes originating form the recipient of a transplant, by di- rect coculturing of lymphocytes from the recipient with TAIC originating from the donor of that transplant. Readministering the cocultivated lymphocytes to the recipient will lead to transplant acceptance by the recipient, as shown in Example 13.

The recipient derived regulatory T-lymphocytes so prepared may be isolated by FACS as described herein (see above) and may be used in a pharmaceutical preparation for preventing transplant rejection in the recipient, wherein the cells are suspended in a pharmacologically acceptable carrier as described above.

The invention is illustrated in further detail by way of exam- ples.

If not defined within the examples, the composition of the me- dia and substances used are as follows: 1. Penicillin/streptomycin solution: 10,000 units of penicillin as sodium salt of penicillin G and 1000 pg streptomycin as streptomycin sulphate per ml physiological sodium chloride solution (NaCl 0,85 %) (Gibco Catalogue No. 15140122).

2. Trypsin-EDTA 0.5 g trypsin and 0.2 g EDTA (4 Na)/l 3. RPMI 1640 (lx, liquid (11875)) contains L-Glutamine RPMI (Roswell Park Memorial Institute) Media 1640 are en- riched formulations, which can be used extensively for mam- malian cells. Components MoL-weight Cone. (mg/1) Motarity (nM) Anorganic salts Calcium nitrate (Ca (N03) 2 4H20) 236 100.00 0.424 Potassium chloride (KCl) 75 400.00 5.30 Magnesium sulphate (MgSO4) 120 48.84 0.407 Sodiumchloride (NaCI) 58 6000.00 103.44 Sodium bicarbonate (NaHC03) 84 2000.00 23.800 Sodium phosphate (Na2HP04) 142 800.00 5.63 Further components Glucose 180 2000.00 11.10 Glutathione, reduced 307 1.50 0.0032 Phenol red 398 5.00 0.0125 Amino acids L-Argmme 174 200.00 1.10 L-Asparagine 132 50.00 0. 379 L-Asparaginic acid 133 20.00 0.150 L-Cysteine dihydrochloride 313 65.00 0.206 L-Glutamininc acid 147 20.00 0.136 L-Glutamine 146 300.00 2.05 Glycine 75 10.00 0.133 L-Histidine 155 15.00 0.0967 L-Hydroxyproline 131 20.00 0.153 L-Isoleucine 131 50.00 0.382 L-Leucine 131 50.00 0. 382 L-Lysine hydrochloride 146 40.00 0.219 L-Methionine 149 15.00 0.101 L-Phenylalanine 165 15.00 0.0909 L-Proline 115 20.00 0.174 L-Serine 105 30.00 0.286 L-Threonine 119 20.00 0.168 L-Tryptophan 204 5.00 0.0245 L-Tyrosine disodium, dihydrate 261 29.00 0.110 L-Valine 117 20.00 0.171 Vitamins Biotin 244 0.20 0.008 D-calcium pantothenate 477 0.25 0.0005 Choline chloride 140 3.00 0.0214 Folic acid 441 1.00 0.0022 i-Inositol 180 35.00 0.194 Niacinamide 122 1.00 0.0081 p-aminobenzoic acid (PABA) 137 1.00 0.0072 Pyridoxine HCl 206 1.00 0.0048 Riboflavin 376 0.20 0.0005 Thiamin HCI 337 1. 00 0.0029 Vitamin B12 1355 0.005 0.00000369 <BR> Reference: Moore G. E. , et al. , J. A. M. A. 199: 519 (1967) 4. PBS (Dulbecco's phosphate buffered saline) cf. J. Exp. Med.

98: 167 (1954): Components g/l KC1 0.2 KH2PO4 0.2 NaCl 8.00 Na2PH04 1. 15 5. Ficoll-Hypaque: Lymphocyte separation medium (saccharose/epichlorohydrin- copolymerisate Mg 400,000 ; Density 1.077, adjusted with So- dium diatrizoate).

6. L-Glutamine Liquid: 29.2 mg/ml 7. Macrophage-colony stimulating factor (M-CSF) Recombinant human M-CSF from E. coli; contains as monomer (18.5 kD) 135 amino acid residues including the N-terminal methionine; is present as a homodimer with a molar mass of 37 kD; (SIGMA Catalogue No. M 6518) 8. y-Interferon (y-IFN) Recombinant human y-IFN from E. coli; 16.7 kD protein con- taining 143 amino acid residues (CHEMICON Catalogue No.

IF002)

Example 1 Separation of Monocytes from whole Blood To avoid the coagulation of the blood and to feed the cells, 450 ml human whole blood was mixed in a triple chamber bag set with 63 ml of a stabiliser solution which contained, per litre H2O, 3.27 g of citric acid, 26.3 of g trisodium citrate, 25.5 g of dextrose and 22.22 g of sodium dihydroxy phosphate. The pH of the solution was 5.6-5. 8.

To separate the components of the blood,"sharp centrifuging" of this mixture was subsequently carried out at 4000 rpm for 7 minutes at 20°C. This resulted in the layering of the corpuscu- lar and non-corpuscular components within three layers. By us- ing the bag set in a compression machine provided for this purpose, the erythrocytes were then pressed into the lower bag, the plasma was pressed into the upper bag and the so- called buffy-coat remained in the middle bag and contained a volume of approximately 50 ml.

The quantity of 50 ml of freshly obtained buffy-coat was then divided into 2 portions of 25 ml each and layered onto 25 ml of Ficoll-Hypaque separation medium respectively which had been introduced previously into two 50 ml Falcon tubes.

This preparation was centrifuged for 30 minutes at 2500 rpm without braking. Thereafter, any erythrocytes and dead cells still present in the buffy-coat were below the Ficoll phase, whereas the white blood cells, including the monocytes, were separated off on the Ficoll as white interphase.

Subsequently, the white interphase including the monocytes was carefully removed by pipetting and mixed with 10 ml of phos- phate-buffered saline (PBS).

This preparation was then centrifuged three times for 10 min- utes at 1800 rpm with braking, the supernatant being removed by pipetting after each centrifuging process and fresh PBS be- ing introduced.

The cell pellets assembled at the bottom of the centrifuging vessel (Falcon tubes) contained the mononuclear cell fraction, i. e. the monocytes.

To prepare the monocytes required for the rat experiments, 25 ml of whole blood were isolated from four genetically identi- cal donor rats respectively and each was layered onto a 25 ml Ficoll-Hypaque separation medium. The procedure was then con- tinued in the same way as described above. Alternatively, analogous separation steps on Ficoll may also be applied to spleen cell suspensions.

Example 2 Propagation and Modification of the Monocytes The cultivation and propagation of the monocytes was carried out in nutrient medium with the following composition: RPMI 1640 medium 440 ml Fetal calf serum (FCS), 50 ml alternatively, AB serum Penicillin/Streptomycin 5 ml Solution Total volume 500 ml The nutrient medium contained 2, 5 ug/500 ml M-CSF.

The monocytes isolated in Example 1 were suspended in a total quantity of 106 cells in 10 ml of the nutrient medium and transferred onto a Petri dish (100 mm in diameter). The Petri dish had previously been filled with pure inactivated FCS and the FCS had been poured off after 24 hours in order to obtain, in this way, a dish coated with FCS.

The Petri dish was covered with the appropriate cover and kept for 3 days in an incubator at 37°C. The cells settled at the bottom of the Petri dish after 24 hours. On day two, the su- pernatant was pipetted off and the Petri dish again filled with 10 ml of fresh nutrient medium.

On day 4,50 ng y-interferon in 10 ml nutrient medium were added and the dish was again closed and kept for a further 48 hours in the incubator at 37°C.

Subsequently, 10 ml of trypsin solution each diluted 1: 10 with PBS were pipetted into the Petri dish. The closed Petri dish was kept for 10 minutes in the incubator at 37°C.

Thereafter, the separation of the cells adhering to the bottom of the Petri dish was carried out with a cell scraper in such a way that the major part (>90%) of the cells floated in the supernatant.

The total supernatant (10 ml of trypsin solution + 10 ml of medium) was pipetted off, combined in a 50 ml Falcon tube and centrifuged for 10 minutes at 1800 rpm. The supernatant was then discarded and fresh nutrient medium (see above) was added to the precipitate (the remaining cell pellet), 1 ml of nutri- ent being added per 106 cells. The determination of the cell count for the determination of the exact dosage took place ac- cording to known methods, compare Hay R. J.,"Cell Quantifica-

tion and Characterisation", in Methods of Tissue Engineering, Academic Press 2002, Chapter 4, S. 55-84.

This cell suspension was centrifuged (1800 rpm, 10 minutes, see above) and the cell pellet were incorporated either into PBS or for application in man into NaCl (physiol. ). Subse- quently, the intravenous administration can take place di- rectly or within 48 hours.

Alternatively, after centrifuging and discarding the super- natant containing trypsin, FCS/DMSO was added as freezing me- dium to the cells and these were deep frozen in a volume of 10 ml.

The freezing medium contained 95% FCS and 5% DMSO. In each case, approximately 106 cells were incorporated into 1 ml of the medium and cooled in the following steps: 30 minutes on ice; 2 hours at-20°C in the pre-cooled Styropor box ; 24 hours at-80°C in Styropor; Storage in small tubes in liquid nitrogen (N2) at-180°C.

Figure 1 shows the phenotypic changes in the antigen expres- sion, determined by flow cytometry, on the monocytes used af- ter cultivation and y-IFN stimulation of the original mono- cytic cells.

Example 3 Use of the Transplant Acceptance Inducing Cells (TAIC) for Preconditioning of the Immune System of the Transplant Recipient The use of TAIC for treating a potential recipient before transplantation offers itself, for example, in the clinical case of a live donation, where it has been clarified in ad- vance of the organ transplantation who the donor will be and who will receive the donor organ.

For this case, the heterotopic heart transplantation was car- ried out in the rat model on male inbred rats of the strain combination LEW [RT1. 1] (in connection with the present inven- tion referred to as"LEW")-> DA [RTl. aVl] (in connection with the present invention referred to as"DA") using the technique described by Ono and Lindsey [Ref. Ono, K. and Lindsey, E. S.

"Improved technique of heart transplantation in rats". J. Tho- rac. Cardiovasc. Surg. 57,225-229 (1969) ]. On day-7 before the transplantation, the DA recipient rats received 106 TAIC derived from LEW monocytes intravenously in 1 ml of PBS. Sub- sequently, the transplantation took place seven days later of a heart taken from the LEW rat strain, which was heterotopi- cally implanted into the abdomen (abdominal cavity) of the DA recipient animal. Since the rat strains used were inbred strains, the TAIC according to the invention expressed identi- cal tissue antigens as the transplanted LEW heart.

For control purposes, a so-called third strain transplantation was carried out. For this purpose, TAIC (106) originating from the same LEW donor animal were injected intravenously into DA animals again on day-7 (i. e. 7 days before the surgical in- tervention). 7 days afterwards, the transplantation of a heart removed from a CAP [RT1. °] (in connection with the present in-

vention referred to as"CAP") rat inbred strain was carried out. CAP rats express the haplotype RT1. C, they are therefore fully MHC-discordant (MHC-different) to the LEW donor animals.

Below, the individual test groups in which a heterotopic heart transplant took place (n=10) are detailed: 1. LEW-> DA; untreated; <BR> <BR> 2. LEW-> DA; 106 LEW derived TAIC i. v. , day-7 before LEW heart transplantation; 3. CAP-> DA; 106 LEW derived TAIC i. v. , day-7 before LEW heart transplantation; 4. CAP-> DA; untreated; 5. LEW-> LEW, untreated; 6. LEW-> LEW, 106 LEW derived TAIC i. v. , day-7 before LEW heart transplantation.

As can be seen from the Kaplan-Meier survival curves of the heart organs (Figure 2A), 9 of 10 LEW hearts were accepted long-term (>150 days) by DA recipient animals whereas CAP third strain hearts were rejected acutely after 6.7 0.8 days. Where no prior administration of TAIC took place, the LEW hearts were also rejected acutely after 7.2 1.0 days.

The rejection of CAP hearts by the immune response stimulated in the DA animal after 6.7 + 0.8 days took place within the same time span as in the untreated control group in which the CAP hearts of DA rats were rejected after 6.9 1.0 days, com- pare group 3 and group 4, respectively. All hearts trans- planted syngeneically in the LEW-> LEW scheme survived long- term (>150 days) irrespective of whether or not the TAIC pre- treatments had taken place. From this, the conclusion can be drawn that TAIC do not put the recipient organism at risk in the sense of a graft versus host disease. Moreover, it is pos- sible to draw the conclusion from this result that the i. v. administration of 106 TAIC 1 week before transplantation opens

up the possibility of inducing long term organ acceptance. The induced tolerance is donor-specific since a corresponding pre- treatment of DA rats with LEW-derived TAIC does not induce tolerance for CAP third strain heart transplants. In the syn- geneic LEW > LEW scheme, the additional administration of TAIC influences neither the survival of the recipient animals nor that of the transplants.

Figure 2B shows the histological evaluation of a LEW alloge- neic transplant on postoperative day (POD) 150, following het- erotopic transplantation into the abdomen of a DA recipient rat. The recipient rat had been pre-treated on day-7 before transplantation with 106 LEW-derived TAIC. The transplant was functioning satisfactorily (strong heart beat) up to the time of its removal from the recipient rat (POD) 150. The his- tological preparation (x40) showed a healthy heart muscle mor- phology, normal vascular endothelial tissue and only minimal infiltration with mononuclear cells without any indication of acute and chronic rejection processes.

Remarkable in this connection is also the fact that donor- derived cells (detected by immunohistochemical detection using LEW-MHC class I-specific antibodies I1. 69) could be detected long-term in the course of a year in the thymus of the DA re- cipient rats. Figure 2C shows a histological preparation of a thymus, removed on POD 150, of a DA rat pre-treated with 106 LEW-derived TAIC. The preparation was labelled with the mono- clonal antibody 11. 69 specific for LEW-MHC class I. As shown in the Figure, administering TAIC leads to the colonisation of the thymus gland where the presentation of donor-derived MHC antigens to the maturing T-cells takes place; small nests of cells can be clearly recognised which can be labelled with the antibody.

Example 4 Detection of Donor-Derived Modified Monocytes in the Recipient The induction of a mixed chimerism by the intravenous injec- tion of the LEW-derived TAIC in the DA animal concerned can be considered as a possible cause of the tolerance induced ac- cording to the invention. A test was therefore carried out to check whether, following the injection of LEW-derived TAIC, more than 5% of cells can be detected in the blood of the re- cipient animal by flow cytometry in the long term (>45 days).

The flow cytometry was carried out as described in the state of the art [Ref. Preffer F. I.,"Flow cytometry"In: Diagnostic Immunopathology, Colvin RB, Bhan AK, McCluskey, RT (eds. ), Ra-<BR> ven Press New York, pp. 725-449 (1994) ]. The detection of the LEW donor cells in the DA recipient blood took place using the monoclonal antibody 11. 69 which specifically detects the LEW- <BR> <BR> MHC class I antigens [see Fandrich F. , et al. Nature Med. 8,<BR> 171-178, (2002) ]. The chimerism data which were determined for 4 of the LEW-> DA transplantations described in Example 3, following the administration of 106 or 104 TAIC/kg x BW re- spectively, in the peripheral blood of the recipient animals are shown in Figure 2D.

Following the injection of LEW-derived TAIC into four DA re- cipient rats not subjected to immunosuppression (106 cells/kg x BW into rats 1-3 and 104 cells/kg x BW into rat 4), rats 1- 3 showed a longer term chimerism (60-80 days) in the DA re- cipient blood, which could be attributed to donor-derived cells. The detection of donor-derived cells took place by flow cytometric determination using the LEW-MHC class I-specific antibody I1. 69 (a monoclonal antibody which binds only to MHC class I positive cells of the LEW strain of rat and does not cross-react with cells of DA strains of rat). Since quasi all

cells of the peripheral blood express MHC class I antigen on the cell surface, the proportion of donor cells in the periph- eral blood of the DA rat can be highly accurately determined with I1. 69. As shown in the graphs in Figure 20, in 3 of 4 animals, more than 10% of the cells express the donor antigen labelled by I1. 69 within the first 6 weeks following the in- travenous injection of the TAIC. After 60 days following in- jection, this proportion of the chimerism in the peripheral blood of these DA rats decreases substantially and disappears completely on day 100. However, this transient chimerism cor- relates closely to the transplant survival of LEW hearts transplanted after double time (i. e. 7 days after TAIC injec- tion) which are no longer rejected in spite of a lack of donor chimerism (after day 100) (rats 1-3 in the example). On the other hand, the induction of short-term chimerism following the administration of 104 cells/kg x BW (Rat 4; <20 days) does not guarantee the long-term transplant acceptance of the transferred heart.

Example 5 Administration of Donor-Derived Cells post transplantationem An evaluation was then to be carried out for the clinical case of corpse (deadbody) donation to determine to what extent the postoperative administration of TAIC was capable of inducing the corresponding long-term acceptance of the transplanted or- gan in the recipient. For this purpose, heterotopic heart transplantations were carried out in the LEW-> DA rat inbred strain model. The DA recipient rats received 4 cycles of cy- closporin A (CSA) intravenously in the dosages of 5 mg CSA/ kg x BW on days 0,1, 2 and 3 following transplantation. On day 7, the intravenous administration of 106 LEW-derived TAIC in- travenously into the tail vein of the DA recipient rats took

place. The following experimental groups served as controls (n=6-10).

1. LEW-> DA; untreated <BR> <BR> 2. LEW-> DA; CSA, 5 mg/kg x BW, i. v. , day 0,1, 2 and 3<BR> 3. LEW-> DA; CSA, 5 mg/kg x BW, i. v. , day 0,1, 2 and 3<BR> plus 106 LEW-derived TAIC, i. v. , day 7<BR> 4. LEW-> DA; 106 LEW-derived TAIC, i. v. , day 7<BR> 5. CAP-> DA; CSA, 5 mg/kg x BW, i. v. , day 0,1, 2 and 3<BR> plus 106 LEW-derived TAIC, i. v. , day 7 The postoperative intravenous treatment of the DA recipient rats with 106 LEW-derived TAIC on POD (postoperative day) 7 leads to long-term tolerance if an initial administration of 4 <BR> <BR> cycles of CSA (5mg/kg x BW, i. v. ) has been effected from day 0- 3. The initial administration of CSA is necessary since the sole treatment with a single administration of 106 TAIC on POD 7 (postoperative day) prevents acute rejection only in 1 out of 6 cases. The CSA dose chosen in this case has only a sub- therapeutic effect since no long-term acceptance can be in- duced by the exclusive CSA administration even though the sur- vival of the transplant is prolonged. The induced transplant acceptance is donor-specific since a corresponding treatment of DA rats with LEW-derived TAIC does not induce any tolerance for CAP-third strain heart transplants.

As shown in Figure 3, the hearts of experimental group 1 were rejected acutely after 7.0 + 0.8 days. The hearts of group 2 were rejected with a delay after 14.4 7.0 days. The hearts of group 3 were accepted for longer than 150 days in 5 out of 6 cases. In the rat system, the acceptance of organs for more than 100 days is considered to be long-term acceptance since the average life expectancy of an inbred rat is only approxi- mately 2 years. The sole postoperative administration of TAIC

(106 cells) was able to prevent acute rejection only in 1 out of 6 cases since the heart organs ceased to beat after 22.6 31.6 days (group 4). The third strain control with CAP hearts showed the specificity of induced transplant acceptance since third strain hearts were again rejected acutely after 7.4 2.2 days. These results also prove that the additional appli- cation of TAIC cannot generate any general immunosuppression which did not prevent the acute rejection to the CAP hearts.

Example 6 Investigation regarding the Organ Specificity of the Long-Term Acceptance induced by TAIC To exclude the possibility of TAIC being able to provide a protective effect against the allogeneically specific immune response directed by the recipient against the donor antigen only for heart transplants, the following organs were trans- planted in the following experimental groups (n=6) in the strongly rejecting DA-> LEW rat inbred system: 1. DA (kidney) LEW; untreated <BR> <BR> 2. DA (kidney) LEW; 106 DA-derived TAIC, i. v. , day-7 and-1 before transplantation 3. LEW (kidney) LEW; untreated 4. DA (liver) LEW; untreated <BR> <BR> 5. DA (liver) LEW ; 106 DA-derived TAIC, i. v. , day-7 and-1 before transplantation 6. LEW (liver) LEW; untreated 7. DA (skin)-> LEW ; untreated <BR> <BR> 8. DA (skin)-> LEW ; 106 DA-derived TAIC, i. v. , day-7 and-1 transplantation 9. LEW (skin)-> LEW ; untreated

As shown by the Kaplan-Meier plots illustrated in Figure 4A-C, 6 out of 6 kidney organs, 5 out of 6 liver organs and 5 out of 6 skin grafts were accepted long term (>150 days) by LEW re- cipient rats. All syngeneic organ transplantations served as controls of the technical execution without complications and were accepted by the donor animal without restriction (not shown in the survival curves). Consequently, these test schemes also show that the intravenous prior injection of 2 x 106 TAIC induces long-term organ acceptance for more than 80% of the transplanted organs.

The kidney-, liver-and skin transplants listed above which were transplanted with and without the prior administration of TAIC were then examined histologically. Figure 4D shows that as a result of the intravenous injection, given twice, of 106 TAIC per kg body weight on days-7 and-1 before transplanta- tion, the morphology of the transplanted kidney can be shown to be intact (compare control kidney and syngeneic transplant LEW-> LEW), whereas, in the untreated allogeneic control group DA-> LEW, a clear infiltration of the transplant in the interstice can be recognised (on postoperative day 14). The allogeneic liver transplant (Figure 4E), which had been fully rejected on POD 12 without TAIC pre-treatment (DA-> LEW with- out TAIC), behaves in an analogous manner whereas the prior administration of TAIC allows the parenchyma of liver trans- plants to appear as being completely homogeneous and intact in comparison with the syngeneic transplant. The allogeneic skin transplant (DA) also heals without complication (compare com- parison with the syngeneic LEW transplant) whereas the CAP third strain graft transplanted simultaneously was rejected acutely as early as on postoperative day 12. This example proves the specificity of the tolerance induced by TAIC since the pre-treatment of the LEW recipient animal with DA-derived TAIC on days-7 and-1 leads to the acceptance of the DA trans-

plant whereas the CAP skin graft transplanted simultaneously on day 0 is acutely rejected (Figure 4F).

Example 7A Investigations regarding the Haplotype Specificity of the Long-Term Organ Acceptance induced by TAIC In order to exclude the possibility of TAIC inducing long-term organ acceptance only in the selected rat inbred strain combi- nation LEW-> DA, the following further inbred strain combina- tions were examined in the heterotopic heart transplant model (n=6). For this purpose, the inbred strain BN [RTl. n] (referred to as"BN"in connection with the present invention) was also used, among others.

1. DA-> LEW ; untreated 2. DA-> LEW; CSA, 5 mg/kg x BW, i. v. , day 0, 1, 2,3 plus 106 DA-derived TAIC/kg x BW, i. v., day 7 and 10 postoperative 3. CAP-> LEW; untreated <BR> <BR> 4. CAP-> LEW ; CSA, 5 mg/kg x BW, i. v. , day 0,1, 2,3 plus 106 CAP-derived TAIC/kg x BW, i. v., day 7 and 10 5. BN-> LEW; untreated 6. BN-> LEW; CSA, 5 mg/kg x BW, i. v. , day 0,1, 2,3 plus 106 BN-derived TAIC/kg x BW, i. v., day 7 and 10 It had already been known from preliminary experiments that in the so-called"high-responder"combination (DA-> LEW), which is associated with the strongest rejection response known in the rat inbred model, no long-term acceptance can be achieved

with the single postoperative i. v. administration of 106 TAIC.

An attempt was therefore made to increase the presence of TAIC in the recipient animal by administering it twice. As shown by the corresponding survival curves illustrated in Figure 5A, the administration of TAIC given twice on postoperative days 7 and 10 provided a long-term organ acceptance in 4 out of 6 cases in group 2 and in 5 out of 6 cases in experimental groups 4. In the BN-> LEW strain combination, all trans- planted organs survived long-term without any indication of an acute rejection. In all cases in which the transplanted hearts had been accepted long term (>150 days), a mixed chimerism could be detected in the recipient animals during the first 20-45 days following the TAIC administration. An early organ failure, however, was always accompanied by a lack of donor cells in the peripheral blood of the recipient. From these data, the conclusion can be drawn that the i. v. administration of TAIC leads to long-term organ acceptance only if the cells induce a mixed donor chimerism which can be detected for at least 21 days. This also confirms the experimental results shown in Figure 2D.

By means of the postoperative administration of 106 TAIC per kg body weight given to the recipient animals intravenously on days 7 and 10, it was consequently possible to induce long- term tolerance in all 3 inbred strain combinations in more than 80% of cases, if, additionally, 4 cycles of CSA were ad- ministered initially.

Example 7B Investigations regarding the Significance of the y-IFN Stimu- lation of M-CSF-treated Monocytes for in vivo Tolerance Induction In order to be able to characterise the efficiency of the ad- ditional stimulation of M-CSF-treated blood monocytes with y- interferon on the tolerance development in vivo in further de- tail, the following test groups were examined in the LEW-> DA rat inbred model for heterotopic heart transplantation (n = 6 animals per group): 1. LEW-> DA; 106/kg x BW LEW-derived blood monocytes (uncultivated monocytes), i. v. , day-7 be- fore heart transplantation 2. LEW-> DA; 106/kg x BW LEW-derived blood monocytes (treated with M-CSF), i. v. , day-7 before heart transplantation 3. LEW-> DA ; 106/kg x BW LEW-derived blood monocytes (stimulated with y-IFN), i. v. , day-7 be- fore heart transplantation 4. LEW-> DA ; 106/kg x BW LEW-derived blood monocytes (treated with M-CSF plus stimulated with y-IFN), i. v. , day-7 before heart trans- plantation As shown by the Kaplan-Meier survival curves of Figure 5B, the intravenous administration of fresh non-cultivated LEW-derived blood monocytes, 7 days before heart transplantation, could not prevent the acute allogeneic transplant rejection of the LEW hearts in the DA donor animal. The transplants of this ex- perimental group were rejected on average ( SD) after 7.8 0.8 days. The prior administration of monocytes cultivated over 6 days with M-CSF, however, resulted in a significant ex-

tension of the organ survival time since, in this experimental group, a rejection was observed on average only after 35.0 51.5 days. The sole stimulation of fresh blood monocytes with y-IFN over 48 hours in RPMI medium containing no M-CSF could not prevent the acute rejection of the heart transplants which ceased to beat on average after 7.8 1.2 days. Only the M-CSF treatment of fresh blood monocytes over 6 days and the addi- tional stimulation of these cells with Y-IFN over 48 hours (on day 5 and 6) led to long-term organ tolerance (> 150 days) in 4 out of 6 transplants. The results show the decisive impor- tance of the additional stimulation of the M-CSF treated mono- cytes with y-IFN for the generation of in vivo tolerance.

Example 8 Investigations regarding the Species Specificity of long-term Organ Acceptance induced by TAIC In order to exclude the possibility of TAIC effectively induc- ing a long-term organ acceptance only in the selected animal species of rat, cells of monocytic origin were isolated from the donor pig in a manner analogous to the method detailed in Example 2, whereby the stimulation with y-IFN was effected by adding 1000 U/10 ml to the nutrient medium over 24 hours. Sub- sequently, the investigation for the effectiveness of TAIC to suppress the acute rejection was carried out in the model of the left side lung transplantation on"SLA-mismatched minipigs"which have a potency to reject their organs compara- ble to that of man. In this case, the left lung of a donor pig is removed and transplanted orthotopically into a genetically different recipient pig (namely into the left thoracic cavity following the removal of the left lung from the recipient pig). At the time of the lung removal, 500 ml of donor blood

was removed simultaneously which served to prepare the TAIC from the monocytes of this pig.

The donor animals all had a weight of 30-35 kg.

The following experimental groups were established in the pig (n=4): 1. CSA, 5 g/day, 50 mg azathioprin/day, 25 mg methyl prednisolone/day, for a total of 28 days 2. As in group 1, plus 108 bone marrow cells (BM) of the do- nor pig/kg x BW recipient pig plus 4.5 Gy whole body ir- radiation (WBI) of the recipient pig 3. As in group 1, plus 106 TAIC derived from the donor pig/ kg x BW on postoperative days 7 and 10 following lung transplantation As shown in Figure 6A, the rejection of the lung transplants in group 1 took place on average 50.3 9.9 days following the termination of immunosuppression. The animals in group 2, on the other hand, rejected their organs after 102.3 81.0 days.

Triple immunosuppression in combination with TAIC treatment repeated twice prolongs the organ survival to 292 135.5 days, 3 out of 4 animals exhibiting a long-term organ accep- tance (>350 days) of their organs. In all cases of group 3, a mixed donor chimerism could be observed in the recipient blood for >21 days, whereas animals of group 1 and 2 exhibited only a short-term mixed chimerism for 6-8 days. Figure 6B shows the lung transplants of a pig of experimental group 1 (POD 41) and a pig treated with TAIC from experimental group 3 (55 days af- ter transplantation; B). Whereas, in a projection with respect to the left thorax wall around the heart silhouette, a visible reduction in transparency (shading) can be seen as an indica- tion of the rejected lung transplantation in the pig of ex- perimental group 1, the thorax x-ray picture of the animal

treated with TAIC shows an x-ray unobtrusive lung and trans- plant finding respectively, with a good delimitation with re- spect to the heart silhouette.

Example 9 Binding of the Antibody GM-7 to TAIC The monoclonal antibody GM-7 was generated by immunising mice with human TAIC which had been prepared as described in Exam- ple 2. The hybridoma cells producing the antibody were depos- ited at the"Deutsche Sammlung fur Mikroorganismen"under the accession no. DSM ACC2542. The results reported below demon- strate that the antibody binds specifically to an antigen which is expressed only on CD14+ cells which had been subjected to the 6 day ex situ modification with M-CSF and 2 day Y-IFN stimulation according to the invention.

Figure 1 shows the binding capacity, determined by flow cy- tometry, of GM-7 to monocytic cells after in vitro modifica- tion, i. e. after transformation into TAIC. It can be seen that the CD14-positive monocytes obtained directly from buffy-coat do not bind the antibody GM-7 (the grey shaded cloud corre- sponds to the antibody control). In contrast, part of the monocytes express an antigen after cultivation in M-CSF and stimulation with y-IFN, which antigen is recognised by the monoclonal antibody GM-7. After cultivation as described in Example 2, about 80% of the transformed monocytes are able to bind the monoclonal antibody GM-7.

In a further experiment, the suppressor activity of the CD14+/GM-7+ cells was compared with that of CD14+/GM-7-cells in a mixed lymphocyte culture (MLC). The MLC was carried out <BR> <BR> as described by Kurnick, J. T. "Cellular Assays"in: Diagnostic

Immunopathology, [Colvin R. B. , Bhan A. K. , McCluskey, R. U.

(ed.), Raven Press, New York, pages 751-771 (1994)].

In this example, the TAIC stem from an individual B. As shown in Figure 7, a significant difference exist between the sup- pressor activity of the GM-7 positive and GM-7 negative TAIC.

Only the GM-7 positive fraction the TAIC population obtained after 6 days treatment with M-CSF and 2 days stimulation with Y-IFN exhibits a significant inhibition effect on the T-cell proliferation activity of responder cells of the individual A after stimulation with cells of B.

These data indicate that, for clinical purposes, a cell popu- lation with optimised suppressor function can be isolated from the TAIC population obtained after cultivation of original monocytes with M-CSF and y-IFN-stimulation through the avail- ability of the monoclonal antibody GM-7.

Example 10 Determination of the Influence of the IDO Inhibitor 1-methyl- tryptophane on the Immunosuppressing Activity of the TAIC In order to clarify, whether the inhibitor of the enzyme indo- lamine-2,3-dioxygenase (IDO) 1-methyltryptophane (1-MT) influ- ences the suppressor function of the TAIC generated in the "Mo"and"Mo+Ly"set ups (see Example 11), a variety of mixed lymphocyte cultures (MLC) with PHA (phytohaemagglutinine) stimulated T-cells in the presence and in the absence of 1-MT were established.

In these mixed lymphocyte cultures 50.000 lymphocytes with 2 pg PHA were transferred into the wells of a 96-well-plate, followed by a proliferation period over 144 hours (indicated

as"PhaLy"). Lymphocytes only cultivated in medium without addition of PHA were run as a further control (indicated as "Ly")- In order to determine the proliferation of PHA-stimulated lymphocytes in the different co-cultures, the following 4 set ups were run and examined: PhaLy +"Mo+Ly"PHA-stimulated lymphocytes and TAIC [105 cells from the set up"Mo+Ly"according to Example 11].

PhaLy+"Mo+Ly"+1-MT PHA-stimulated lymphocytes and TAIC in the presence of 2 J. mol 1-MT [105 cells from the set up"Mo+Ly"according to Ex- ample 11].

PhaLy +"Mo"PHA-stimulated lymphocytes and TAIC [105 cells from the set up"Mo"according to Example 11].

PhaLy+"Mo"+1-MT PHA-stimulated lymphocytes and TAIC in the presence of 2 pmol 1-MT [105 cells from the set up"Mo"according to Example 11].

After 144 hours cultivation, all controls or co-cultures were <BR> <BR> further cultivated for 24 hours in the presence of 3 [H] - thymidine ("pulsed") and thereafter the amount of radioac- tively labeled thymidine incorporated was determined as counts per minute (cpm), see Figure 8. In this arrangement, the amount of the radio activity determined is a measure for the amount of labeled thymidine incorporated into the DNA, and therefore a measure for the proliferation rate of the

lymphocytes. The values reported in Figure 8 correspond to mean values from triple determinations of 3 experiments each with indication of the standard deviation.

The results demonstrated that lymphocytes not stimulated with PHA ("Ly") do not significantly proliferate, the mean radio- activity observed being 367 cpm (see Figure 8). In contrast, the stimulation with 2 pg PHA leads to a significant increase in the proliferation rate of the lymphocytes ("PhaLy"), the highest incorporation being measured at a mean value of 18459 cpm in these samples.

The addition of TAIC to the lymphocyte cultures clearly de- creased the proliferation rate strongly if cells from the set up"Mo+Ly"from Example 11 were added (PhaLy +"Mo+Ly", de- termined value 1498 cpm), and less strongly when cells from the set up"Mo"from Example 11 were added (PhaLy +"Mo", measured value 3369 cpm).

The results obtained after addition of 2 pmol 1-methyl- tryptophane (1-MT) to the set ups containing"Mo+Ly"and"Mo" with stimulated lymphocytes demonstrated that 1-methyl- tryptophane (1-MT) increases the suppressor function of the TAIC synergistically, whereby the decrease was stronger with the TAIC from the set up"Mo+Ly" (measured value 267cpm) than with the TAIC from the set up"Mo" (measured value 390 cpm).

Example 11 Influence of Lymphocytes on the Formation of CD3+/CD14+-Cells during Monocyte Cultivation The influence of lymphocytes present in the monocyte fraction

on the generation of CD14+/CD3+-cells effective as TAIC was de- termined by comparison of two different set ups.

For the first set up (subsequently indicated as"Mo") the monocyte fraction was initially taken from the interphase of the buffy-coat as described in Example 1. As described in Ex- ample 2, the cells were subsequently transferred to the culti- vation step with M-CSF. Within one hour after the starting point of the cultivation, the monocytes adhering to the bottom of the tissue culture flask were washed five times with 10 ml PBS each, and the amount of the lymphocytes present in the culture was thereby decreased to < 5 % (4,8 2,4 %), while the amount of enriched monocytes (CD14+) so obtained was above 90 % (92 + 5.6 %). Additional cell components within the set up were B-lymphocytes and granulocytes.

The cells in the second set up (subsequently indicated as "Mo+Ly") were also taken from the interphase of the"buffy- coat"as monocyte fraction as described in Example 1. However, different from set up"Mo"the cells adhering to the bottom of the tissue culture flask were only washed once after 24 hours starting from the beginning of the cultivation phase, as de- scribed in Example 2. As a result, a cell population was ob- tained, which was composed of 45 5,3 % CD14+-monocytes and 23,5 8,9 % CD2+-lymphocytes. As in set up"Mo"lymphocytes and granulocytes were also present in this set up.

The determination of the amounts of the respective cell types in the total cell population per set up was carried out through flow cytometry of three experimental set ups each (see Figure 9). The results are reported as mean values including the standard deviation.

CD14+/CD3+-cells can neither be determined in the set up"Mo"

nor in the set up"Mo+Ly"at the beginning of the culture (d 0 = day 0). After a cultivation period of five days, the experi- ment was terminated and the cells were characterised by FACS- analysis after detaching the cells from the bottom of the tis- sue culture flask as described in Example 2. It was found that the relative amount of CD14+-cells decreases in these set ups, from 92 % to 42 % in set up"Mo"and from 45 % to 28 % in set up"Mo+Ly". Seemingly, the lymphocytes proliferate quicker than the monocytes; the relative amount of lymphocytes in- creased in set up"Mo"from 4,8 % to 69,8 % and in set up "Mo+Ly"from 23,5 % to 50,6 %. During the cultivation, CD14+/CD3+-cells effective as TAIC are formed in both cultures.

It is important in this context that a significantly higher increase in CD14+/CD3+-cells is observed in the set up"Mo+Ly" with an amount of 32,0 5,3 % as opposed to set up"Mo"with only 7,2 3,2 %.

These results demonstrate that the purification of the cells for enrichment of monocytes to a relative amount of more than 90 % at the beginning of the cultivation has a negative influ- ence on the generation of the immuno suppressive CD14+/CD3+- cells in the TAIC population, while the method described in Examples 1 and 2 leads to a significantly higher yield of CD14+/CD3+-cells.

Example 12 In vitro co-cultivation of human TAIC with allogeneic lympho- cytes for generating regulatory T-cells To examine whether TAIC induce the formation of regulatory T- cells, i. e. CD4+/CD25+-lymphocytes, in the recipient, several different in vitro cultures of TAIC with lymphocytes, were

run and the formation of regulatory T-cells resulting there- from was analyzed.

For this purpose, TAIC of donor A were directly or indirectly co-cultivated in vitro together with lymphocytes of a donor B. In the direct co-culture, the direct cell-to-cell-contact between the TAIC (of donor A) and the lymphocytes (of donor B) was made possible, while in the indirect co-culture a mem- brane ("cell culture insert", 0,4 m pore size, Falcon, order no. 353090) allowed exchange of the medium, but inhibited the physical contact of the two cell populations. The direct or indirect co-culture is carried out for preferably 3 to 5 days, more preferably for 4 days under incubator conditions i. e. at 37°C and in a 5% C02 atmosphere.

After culturing, the respective numbers of regulatory T-cells (CD4+/CD25+) were determined in both set ups as well as in the controls, wherein TAIC or lymphocytes respectively were cul- tivated alone. Further, the number of CD3+/CD14+-cells, which represent the component of the TAIC-cell population having the most significant suppressor function in the mixed lympho- cyte culture, was determined in the control set up, wherein the TAIC were cultured alone.

In all set ups, the surface antigens of the cells were deter- mined per FACS analysis and the amount of the respective cell populations in the total amount of the cells was analysed.

Further, the relative expression of three new master genes specifically expressed by regulatory T-cells (Foxp3, CTLA-4 and Integrin (XEP7) was determined by PCR in the respective cell population (see Table). Foxp3 is a specific transcrip- tion factor, which is viewed as a control gene for the devel- opment of regulatory T-cells, and which is specifically ex-

pressed by these cells [see Hori, S. et al. ,"Control of Regulatory T-cell Development by the Transcription Factor Foxp3", Science 299,1057-1061 (2003) ].

CTLA-4 is a further factor, which is used as a marker for the determination of the regulatory function of CD4+/CD25+-T-cells (see Khattri, R. et al.,"An essential role for Scurfin in CD4+/CD25+ T regulatory cells", Nature Immunology, online pub- lication, doi: 10. 1038/ni909 (2003) ; Shimizu, J. et al.

"Stimulation of CD25+/CD4+ regulatory T cells through GITR breaks immunological self-tolerance", Nature Immunology, on- line publication, doi: 10.1038/ni759 (2003); Cobbold, S. P. et <BR> <BR> al. "Regulatory T cells in the induction and maintenance of peripheral transplantation tolerance", Transpl. Int. 16 (2), 66-75 (2003)].

Integrin (XEP7 is an integrin, which binds to epithelial Cath- erine and which may be used as a marker for the most potent sub-population of regulatory CD25+-T-cells [see Lehmann, J. <BR> <BR> et al. "Expression of the integrin aE (3 identifies unique sub- sets of CD25+ as well as CD25-regulatory T cells"PNAS 99 (20), 13031-13036 (2002)].

The determination of Foxp3-, CTLA-4-and integrin meß7- expession was carried out by means of quantitative PCR using GAPDH and 0-action, two"housekeeping genes", as controls ; the values determined were, on the one hand, placed in relation- ship to each other, the value obtained for the CD14+/CD3- cells being set at 1 ; on the other hand the absolute RNA amounts were indicated in jug per g total RNA, in order to correlate the measured suppression effected by the TAIC in vitro and the formation of the CD4+/CD25+ double positive cells with the expression rate of the respective genes. Stan- dard methods were used for the quantitative PCR, which are

known to the skilled person (see Lottspeich, F. , Zorbas, H.

"Bioanalytik", Spektrum Akademischer Verlag GmbH, Heidelberg- Berlin, 1998).

The Table shows that within the population of lymphocytes ob- tained from the direct co-culture, the percentage of double positive cells CD4+/CD25+ increases manifold to a value of 8,7 % in comparison to the amount of CD4+/CD25+ lymphocytes ob- tained from the indirect co-culture or control, which is nearly identical with 2,38 % and 2,65 % respectively.

The sub-population of CD4+/CD25+ cells expresses the highest relative amounts of mRNA from all tested mastergenes as com- pared to the expression in CD4+/CD25-cells (see Table). While the expression of Foxp3 is increased by about a factor 10 (37 versus 3,75), CTLA-4 expression reaches an even higher maxi- mum expression (4699 versus 0,376). The increase of expres- sion of the third mastergene integrin aEß7 in the CD4+/CD25+ cells during co-culturing is nearly as high as for CTLA-4 since the absolute amount of integrin aEß7 mRNA is raised to 1,4 x 10-9 in CD4+/CD25+ cells as compared to 3,4 x 10-12 ug mRNA/ug total RNA in CD4+/CD25-cells.

After indirect co-culture, the relative amount of Foxp3-mRNA in the CD4+/CD25+ sub-population amounts to only 10 and is nearly as low as the relative amount expressed by the lympho- cytes of the control, which expresses a relative amount of Foxp3-mRNA of 15.

The relative amount of CTLA-4-mRNA expressed by the lympho- cytes of the control is as low as 0,375 in the CD4+/CD25+- population and 0,1 in the CD4+/CD25-population. Control direct co-indirect co- culture culture TAIC lymphocytes lymphocytes lymphocytes CD14+/CD14+/CD4+/CD4+/CD4+/CD4+/CD4+/CD4+/ CD3 CD3-CD25+ CD25 CD25+ CD25-CD25+ CD25- FACS 41 20 2, 65 30, 8 8, 7 49 2, 38 27, 6 [% positive cells] relative 50 1 15 1,5 37 3,76 10 1,5 Foxp3- expression [PCR] absolute 1, 6x10-8 3, 2x10-"' 4, 8x10-9 8x10-"'1, 2x10ro 1, 2x10-' 3, 2x10-' 4, 8x10-"' RNA- amount Foxp3 relative 12500 1 0, 375 0, 1 4699 0, 376 CTLA4- expression [PCR] absolute 6, 5x10-6 5,2x10-10 1,9x10-10 2,4x10-6 1,9x10-10 5, 2x10''" 2, 4x10° 1, 9x10''" RNA- amount CTLA4 absolute 3, 4x104 not 1, 4x10~9 3, 4x10-" RNA-detect- amount able Integrin aEp7 Table: Determination of the amounts of specific cell popula- tions in the total amount of cells after direct and indirect co-culture by reference to their surface markers CD3, CD4, CD14, CD25, and determination of the relative expression and the absolute amounts of RNA of three genes (Foxp3, CTLA-4 and integrin aEa7) in these cell populations.

The expression of CTLA-4 in the CD14+/CD3+ sub-population of the TAIC cells was similar to the expression of Foxp3 and was also significantly higher than in all other cell populations.

In this regard, it is noteworthy that the CTLA-4 expression (relative value of 12.500) was manifold stronger in the CD14+/CD3+-sub-population than the Foxp3-expression, which ex- hibited a relative value of 50.

No expression of the integrin asp was detectable in the CD14+/CD3-sub-population of the TAIC, while similar to the behavior of the expression of the other two analyzed genes, the expression of the integrin in the CD14+/CD3+-sub- population of the TAIC, measured as absolute value in pg RNA per pg total RNA, reached the highest value (3,4 x 109 ug/ug total RNA).

The significantly increased expression of the three lympho- cyte markers Foxp3, CTLA-4 and integrin aEP7 on the TAIC de- rived from monocytes as compared to normal lymphocytes is to- tally unexpected and has to date never been observed on mono- cytes or on cells derived from monocytes.

In conclusion, the results of this Example as shown above demonstrate the following: If one starts from the assumption that the level of Foxp3-, CTLA-4-, and integrin 07-expres- sion correlates with the immunoregulatory properties of the respective cells, it was demonstrated here, that the suppres- sor activity of the CD3+/CD14+ sub-population of the TAIC is associated with a high expression of these three genes. This is even more surprising when it is considered that these markers have to date only been described for lymphocytes, but never in cells of monocytic origin.

It was further shown that the direct co-culture of TAIC with lymphocytes leads to a significantly higher amount of CD4+/CD25+ lymphocytes as compared to indirect co-cultivation and the cultivation of only lymphocytes. This supports the

assumption that also in vivo (i. e. in a patient) regulatory T-cells are formed after administration of TAIC. These re- sults are in conformity with the known immunoregulatory func- tion of CD4+/CD25+ lymphocytes and with the fact, that the contents of Foxp3-, CTLA-4-, and integrin aEP-mRNA in these cells are significantly higher than in indirect co-cultivated lymphocytes or in control lymphocytes.

Example 13 In vivo Induction of Transplant Tolerance by Lymphocytes co- cultured with TAIC in vitro The results and conclusions presented in Example 12 were con- firmed in vivo in an animal experiment. Different from the procedure described in Examples 3,4, 5,6 and 7, the animals in the selected LEW->DA Inbred combinations were not injected with LEW-derived TAIC for induction of tolerance, but DA- lymphocytes from the recipient which, over a period of 5 days, were previously directly co-cultivated (LEW) -derived TAIC from the donor, or which were cultivated alone in medium as con- trols, were injected to the animals in this example.

Animals, which received autologous co-cultivated DA- lymphocytes prior to an allogeneic heart transplantation, de- veloped donor specific tolerance, whereas control animals, which received naive non-cocultivated control DA-lymphocytes, acutely rejected the transplanted heart within 10 to 14 days.

These results indicate that the physical cell to cell interac- tion between donor-TAIC and recipient-lymphocytes induces the generation of regulatory T-cells, which, per se, are capable of modifying the syngeneic immune system of the recipients such, that potentially alloreactive T-cells are suppressed and the organ rejection is thereby prevented.

INTERNATIONAL FORM University of Kiel <BR> <BR> Depc. of General & TDorscic Surery<BR> Arnold-Hellr-Str.' 24105 Kiel RECEPT IN THE CASE OF AN ORIGINAL DEPOSIT issucd pursuant to Rule 7.1 by the INTERNATIONAL DEPOSITARY AUTHORITY identified at the bottom of this page w t CATtO>t OF : MiF wCRoORCb ideufianomsfGrcrte iven by the DEPOSITOR : Acccsaion numberivan by the -..- OTEiA'nONALDEPOSn'ARYAUTHORTTY GM-7 DSM ACC2542 U. SC, . ? ¢ CDESCR PTlONANjO/R. » OPOSCDTAXONOMICDESIGNATION nee. mcroorganum dennfied und I. aEoYe waS sctomoaoied by : (X a scietttitic dcripcion () a oroooscd anunomic desynuiou rmarc setil tL enz erc appliekbic). AND ACCEPTANCZ Ths ; nternsnonal Deposirry Authonty aecepcs tle micreorbamsm idenoticd under 1. obove. wnicn was rc : : ived by it on 2002-05-13 (Dae. oF he ocigins acpos4'. tv k=CL 'T OF 0. EQUEST FOR CNVERS (ON ? 1, : uc. ^orgamsm asnti : ico undcr t obove w rcceivcd by chie Inemoionai Deaocita rwchonry on (datc ofonpntt depesit) ond a r,. qucst ; o convert thc aneinai depesit :. ^.. : : eposi under Uto Budapa Trcacy woc received by it on (date ol reeeipt eireqant fbrdnvcnion) V (NiLe'tNA'i ? ONALpEPOSI1ARYAUh30QITY Ntame : DSMZ-DEUrSC : fE SAMMLUNC VON Signmvtr (t) of Deteon (s) having the powcr to represent the MtLK. 200O . Go, TtISMEN UND ZL'LLKUL1'r'REN Gmol Incernuioot) Depoutacy Autlionry or of auhonzsa officia (e) : Ac14czs : M ascherodcr Weg I b D-7S1 a Drsuaschwug De : 2002w0S-22 ,.

INTERNATIONAL FORM University of Kiel Dept. of General & Thoracic Surery <BR> <BR> . old-Heller-Str. î<BR> 24"-. 05 Kiel VIABILITY STATEMENT issues durant to Rule 10.2 by the INTERNATIONAL DEPOSITARY AUTHORITY identified at the bottom of this pojjc i. oEPOsrroR n. ErmF ! CA-no or THE MtCROOMAiSM Name : Unimzity of Kie Accossion num6ar given tiy thc. Depc. of General &-horacic Surery uTERNATIONAL DEPOSIf. ARY AUTFIOFITY Addces : q, nold-HrllerSw. 7 24 105 Kief Daie oC the deposic or the cnnsfer' 2002-05-13 n VTA3 ; 1* S-ATE) VJENT The wshlliry of rilc mieroor6anlsm idcntifico undcr Tl sbovc wss tCsX L on 2002 05-13 On Lha, =x. : he said micmorg3misni % va : x), viabic no longer viable N. CONDiTIOlsTS L'NDER wi-nC ! THE VfABtUTYTEST HAS BE PiFOMEy "I V ' ? ) ATIONAL DEPOStTAY AUTWOrrY OSMZ. DEU7SCIC- VON Si7nsrjrc (s) of uc-son (s) liaving Inc power to rcpTeser. (C. IC . QIKAQORGANISMEN UIdD LLL1 : ULT&EN GmbH Guemauunai Dcnositry Authonry or of amhonzed otlicial (s) : Addr. sa : Msasseheroocr Vcy Ic D-33124 Brnunschwug Due : 2002-05-22 @@@ofthe etansrer),<BR> In the cases referred to in Rule 10.2 (a) (ii) and (iii), refer to the most recen viability test Mark with a cross the appticablc box.

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