FC-GAMMA-RII ON HUMAN B-CELLS CAN MEDIATE ENHANCED ANTIGEN PRESENTATION

The ability of Fc gamma R on monocytes and macrophages to enhance pres entation of Ab-bound Ag has been well established. In contrast, studie s suggest that Fc gamma RII on B cells functions primarily to suppress B cell responses. We found that presentation of tetanus toroid (TT) b y human EBV-transformed B cells was enhanced by 100- to 1000-fold, whe n TT was targeted to Fc gamma RII on B cells by using a conjugate cons isting of TT covalently linked to anti-human Fc gamma RII mAb 41H16. T his enhanced presentation could be blocked by mAb 41H16, heat-aggregat ed human IgG, or anti-MHC Class II mAb. Similarly, multimeric immune c omplexes composed of rr and anti-TT mAb, SA13, and 9F12 also enhanced presentation of TT. Furthermore, Fc gamma RII on purified human periph eral blood B cells could also enhance Ag presentation. These studies p rovide the first clear evidence that Fc gamma RII can participate in e nhanced Ag presentation by human B cells, and suggest that Fc gamma RI I has the potential to play a stimulatory role in human B cell respons es to Ag-Ab complexes. (C) 1996 Academic Press, Inc.