Role of Fc receptors in IgA-mediated killing.

Fc receptor–blocking antibodies My43 (FcαRI), 197 (FcγRI), AT10 F(ab′) (FcγRII), or 3G8 F(ab′)2 (FcγRIII) were used to identify which Fc receptor triggered ARH-77 killing by chimeric IgA1 or IgA2 versions of HLA class II antibody F3.3. PMNs served as effector cells. All Fc receptor antibodies were used at 10 μg/mL. As demonstrated, IgA-mediated lysis was completely inhibited by FcαRI antibody, but not by antibodies directed against Fcγ receptors. Data are presented as mean percentage specific lysis ± SEM from experiments with 4 different donors. Significant inhibition (P < .05) is indicated by an asterisk (*).