Antibody-complement-mediated cytotoxicity is enhanced by ribosome-inactivating proteins.

The antibody-mediated cytotoxicity of complement can be increased by the ribosome-inactivating proteins gelonin and PAP-S. Treatment of human lymphoid cells that express CALLA with an anti-CALLA monoclonal antibody, J5, and then with rabbit complement, leaves about 6% of the cells alive. The same treatment in the presence of a sublethal concentration of gelonin or PAP-S leaves only about 0.02 and 0.3% of the cells alive respectively. This synergistic effect has potential implications for the in vitro elimination of malignant cells or of immunocompetent cells from bone marrow before its transplantation.