Multiple reactivities of cytotoxic monoclonal antibodies against pancreatic islet cells.

Since multiple mechanisms of antibody induced cellular killing have been described and since the mechanisms of complement augmented antibody-dependent cellular killing are poorly understood, we investigated the specificities of several monoclonal antibodies. Four murine monoclonal anti-rat pancreatic islet antibodies were evaluated for complement-dependent antibody-mediated cytotoxicity, antibody-dependent cellular cytotoxicity and complement-augmented antibody-dependent cellular cytotoxicity. Although all monoclonal antibodies were selected for islet binding properties, only 1 antibody mediated all 3 mechanisms of killing. Another monoclonal antibody which did not induce complement-dependent antibody-mediated cytotoxicity was effective in the complement-augmented antibody-dependent cellular cytotoxicity assay. These studies indicate functional multiple activities of monoclonal antibodies to islet target cells.