Quantitative contributions of IgG, IgM and C3 to erythrophagocytosisand rosette formation by peritoneal macrophages, and anti‐opsoninactivity of dextran sulfate 500

Abstract

In vitro phagocytosis by guinea pig peritoneal macrophages of immune complexes (EA) was shown to be dependent on IgG antibody in a dosedependent fashion. C3b enhanced phagocytosis of EA at limited IgG antibody concentrations only. When IgM antibody was used for sensitzation ofsheep red blood cells (SRBC), phagocytosis and rosette formation did notoccur in the absence of bound C3. The polyanion, dextran sulfate 500 (DS), was shown to depress both rosette formation and phagocytosis of EA_IgG, EA_IgGC1423 and EA_IgMC1423, as well as immune adherence of human group 0 erythrocytes and hemolytic activity of C3. This effect of DS was seen only when it was actually present in the incubation medium.