Monoclonal antibody to a human salivary gland adenocarcinoma cell line: augmentation of antibody-dependent cell-mediated cytotoxicity activity by streptococcal preparation OK-432 in human salivary gland adenocarcinoma-bearing nude mice given the antibody.

An IgG2a mouse monoclonal antibody (MoAb) to the human salivary gland adenocarcinoma cell line HSG, 5B/10, has been generated in our laboratory. In the current study, the antitumor effects mediated by MoAb 5B/10 in human salivary gland adenocarcinoma (HSG)-bearing nude mice or the antibody-dependent cell-mediated cytotoxicity (ADCC) against HSG cells using human peripheral blood mononuclear cells (PBMC) as effector cells were examined. In addition, effects of the streptococcal preparation OK-432 on the growth of HSG tumors or on the MoAb 5B/10-mediated cellular cytotoxicity were studied. MoAb 5B/10 mediated an ADCC reaction against HSG cells that were insensitive to NK cells but not to the reaction of antibody and complement-mediated cytotoxicity. The coexistence of MoAb 5B/10 and OK-432 caused marked augmentation of cytotoxic effects. Treatment of OK-432-stimulated PBMC with antiasialo Gm1 antiserum plus complement but not with silica particles resulted in a significant decrease of cytotoxic effects as compared with relevant controls. the nude mice inoculated intraperitoneally with HSG cells and treated with MoAb 5B/10, OK-432, or (especially) a combination of the two had significantly prolonged survival times as compared with untreated controls. Moreover, spleen cells from the tumor-bearing mice treated with OK-432 alone or a combination of MoAb 5B/10 and OK-432 were found to carry high levels of effector cell activity in the MoAb 5B/10-mediated cytotoxicity assay using HSG cells as targets.