To obtain the subject new DNA consisting of a DNA containing specific base sequences encoding a variable region of a heavy chain of an anti- Fas antibody, and used for producing an antibody useful for the treatment and diagnosis of an autoimmune disease by inducing the apoptosis of autoantibody producing cells, etc.

This DNA encoding a variable region of an anti-Fas antibody is a new DNA containing base sequences expressed by formulae I to III, and used for the production of the anti-Fas monoclonal antibody useful for the treatment, diagnosis, etc., of an autoimmune disease by inducing the apoptosis of autoantibody producing cells remaining in a living body for removing these cells. The DNA is obtained by culturing a hybridoma CH-11 (FERM P-15708) producing the anti-Fas monoclonal antibody in a medium, preparing mRNA from the cells by a usual method, synthesizing a single-stranded cDNA by using the mRNA as a mold, and amplifying the cDNA by a PCR method using primers encoding the parts of the variable regions of heavy and light chains of the monoclonal antibody.