PURPOSE: To obtain a monoclonal antibody which reacts specifically with a B type antigen only, by a method wherein a splenic cell is sampled from an animal immunized by a human B type red blood cell to form a fused cell between the splenic cell and a myeloma cell and then, a cell stock is cultured to produce an anti-B monoclonal antibody therefrom.

CONSTITUTION: A mouse which is found to contain no B antigen or a very few if any by a agglutination blocking test using saliva or an absorption test using red blood cell is used and it is immunized with a 10% human red blood cell solution at a rate of 0.5ml per dose four times at intervals of 3 days by an abnominal injection. The spleen of the mouse is extracted to sample a cell on the 4th day from the final immunization. A stainless mesh is used for the sampling of the cell. NS-1 is used as mouse myeloma cell to be mixed with the splenic cell and the supernatant is removed by a centrifugal separation. Then, BEG and RPM-1640 as medium is applied to the mixed cell mass to form a fused cell, which is caltured on a HAT medium to produce an anti-B monoclonal antibody.