Functional Mimicry of an Anti‐idiotypic Antibody to Nominal Antigen on Cellular Response

One concept for immune therapy of cancer involves induction of antigen mimic antibodies to trigger the immune system into a response against the tumor cells. Anti‐idiotypic antibodies (Ab2) directed against the antigen‐combining site of other antibodies (Ab1) may functionally and even structurally mimic antigen and induce anti‐anti‐idiotypic immune response. We report here the generation of murine monoclonal antibody (mAb) WJ02 (Ab2) raised against the murine monoclonal immunoglobulin MJ01 (Ab1), which defines ovarian cancer antigen CA125. In enzyme immunoassays the binding of Ab2 to the variable region of Ab1 could be inhibited by CA125. In addition, the mimicry of mAb WJ02 to CA125 on cellular immune response was detected by human peripheral blood cells. The T cells primed by mAb WJ02 or CA125 proliferated in the presence of CA125 or mAb WJ02, respectively. Furthermore, T cells specific to mAb WJ02 could lyse ovarian cancer cells OVCAR‐3 that express CA125. Finally, we proved that a patient immunized with mAb MJ01 could induce T cells that recognize mAb WJ02. In summary, we conclude that mAb WJ02 mimics CA125 on cellular response and such functional mimicry is one of the most important criteria to select Ab2 for cancer therapy.