AUGMENTATION BY BISPECIFIC F(AB')2 REACTIVE WITH P-GLYCOPROTEIN AND CD3 OF CYTOTOXICITY OF HUMAN EFFECTOR-CELLS ON P-GLYCOPROTEIN POSITIVE HUMAN RENAL-CANCER CELLS

A bispecific F(ba')2 was constructed that was composed of two Fab fragments, one derived from anti-CD3 monoclonal antibody (mAb) (OKT3) and the other from anti P-glycoprotein mAb (MRK 16). This bispecific F(ab')2 enhanced the binding and cytotoxicity of human peripheral blood mononuclear cells (PBMCs) on P-glycoprotein-positive human kidney cancer cells (ADMHK/E). It had no effect on the cytotoxicity of PBMCs on P-glycoprotein-negative HK/E cells [long-term cultured HK/E (LCHK/E)]. Control F(ab')2 composed of OKT3 or MRK16 alone did not influence the cytotoxicity of PBMCs on ADMHK/E cells. These findings suggest that the MRK16-OKT3 bispecific F(ab')2 may be therapeutically beneficial in treatment of human multidrug-resistant cancers.