Polymorphonuclear leukocytes-mediated lysis of A431 cells induced by IgG1 mouse anti-epidermal growth factor receptor monoclonal antibodies

The ability of different Fc receptors (Fcγ R) on IgG-mediated cytotoxicity for human epidermoid carcinoma A431 cells bearing large number of epidermal growth factor receptors (EGFRs) was examined by using two isotypes (IgG1 and IgG2a) of murine monoclonal antibodies (MoAbs) against EGFR in the presence of human monocytes and granulocytes. Two MoAbs (225 and LA1) of the IgG1 isotype exhibited effective cytolytic activity for A431 cells with human polymorphonuclear leukocytes (PMN) rather than with human mononuclear cells (MNC). In contrast, two MoAbs (528 and 579) of the IgG2a-isotype lysed the cells less effectively with PMN than with MNC. Anti-Fcγ R II (CDw32) MoAb 2E1 inhibited the IgG1-mediated cytotoxicity by PMN, and anti-Fcγ R III (CD16) MoAb 80H3 did not inhibit the IgG2a-mediated cytotoxicity by MNC. Under these conditions, antibody-dependent cell-mediated cytotoxicity by mouse MoAb IgG1 isotypes resulted from antibody binding to the Fcγ R II (CDw32) of PMN.