Evidence for two distinct Fc receptors on guinea pig peritoneal macrophages

Abstract

Fcreceptors of guinea pig peritoneal macrophages for homologous IgG1 and IgG2 antibodies were found to be solubilized by treatment of the cells with Nonidet P-40, since the soluble fraction obtained inhibited the binding reactions of complexes of IgG1 and IgG2 antibodies with ovalbumin to the intact cells. The solubilized Fc receptors for IgG1 and IgG2 antibodies were indistinguishable from one another by means of gel filtration on a column of Sepharose 6B in the presence or absence of the detergent. Both of the Fc receptors were almost completely removed by affinity chromatography on a column of IgG2-bound Sepharose 6B. Affinity chromatography on a column of IgG1-bound Sepharose 6B, however, showed that the Fc receptor for IgG1 antibody was also almost completely adsorbed, though about 50% of the Fc receptor for IgG2 antibody remained unbound. These results demonstrate the existence of two distinct Fc receptors on guinea pig macrophages; one binds to IgG2 antibody alone and the other bind IgG2 as well as IgG1 antibodies.