The expression of Fc receptors on guinea-pig peritoneal macrophages and neutrophils.

The equilibrium binding of soluble complexes of guinea-pig anti-dinitrophenyl IgG1 or IgG2 and dinitrophenylated bovine serum albumin (DNPBSA) to homologous peritoneal macrophages and neutrophils has been compared. The immunoglobulin receptors on these phagocytes were found to differ in two major respects. Macrophages express specific binding activity for both IgG1 and IgG2 complexes whereas neutrophils possess specificity only for the IgG2 subclass. Furthermore, the number of receptors for IgG2 on macrophages (0.8-1 x 10(6)) is fifty- to seventy-fold greater than the number on neutrophils (1.3-2.6 x 10(4)). The phagocytes also displayed differences in their avidity for soluble IgG2-containing complexes which could either reflect the disparity in receptor densities on their membranes or indicate differences in the structure of their Fc receptors. Inhibition of complex binding by immunoglobulin fragments indicated that, at least, the macrophages and neutrophils recognize the same portion of the IgG2 molecule.