Cloning of antigen 2D7 has been carried out to identify an antigen relevant to antibody 2D7. As a result, it has been found that the antibody 2D7 recognizes HLA class IA. Further, whether or not the antibody 2D7 has cell death inducing activity has been studied. As a result, it has been found that nuclear fragmentation is observed by crosslinking of the antibody 2D7 with another antibody to thereby bring about induction of cell death. Still further, it has been found that a diabody of antibody 2D7 exhibits very strong cell death inducing activity even when any other antibody is not added. These results suggest that an antibody with lowered molecular weight among antibodies capable of recognizing HLA can be utilized as a cell death inducer.