Inhibition of the Fc receptor of human lymphoid cells by antisera-recognizing determinants of the hla system.

The inhibitory effect of HLA antisera on Fc receptors of human lymphoid cells was investigated. The ability of lymphoid cells to form rosettes (FcRFC) with antibody-coated sheep red blood cells and to function as effector cells (K cells) in antibody-dependent cell-mediated cytotoxicity were used as assay systems. We found that antisera recognizing determinants of the HLA-A, -B, and -C series had no effect on FcRFC, while a specific inhibitory effect was observed of antisera probably reacting with determinants identical to or closely associated with those of the HLA-D series. This inhibitory effect was retained in the F(ab')2 fragments. Specific inhibition of K cells was observed with all HLA antisera, but this effect was lost in the F(ab')2 fragments. We conclude that the Fc receptor of rosette-forming lymphocytes may be closely associated with products of the HLA-D region. This is analogous to the association between the Fc receptor and the Ia antigens on murine rosette-forming B lymphocytes.