Superoxide Anion Production from Guinea Pig Macrophages Stimulated with Immune Complexes of Different IgG Subclasses

Abstract

Guinea pig peritoneal macrophages produced superoxide anions (O₂^-) when reacted with ovalbumin complexes of homologous IgGI and IgG 2 antibodies. In this reaction, IgG 2 complexes were about three times as active as IgG 1 complexes. But the susceptibility of IgG 1 complexes to phagocytosis by the cells appeared to be indistinguishable from that of IgG 2 complexes. The avidity of IgG 1 complexes in the antigen excess zone for Fc receptors on the cells was lower than that of the IgG 2 counterparts. The amount of IgG 1 complex bound to the cells, however, did not significantly differ from that of IgG 2 complex when compared using each complex at the equivalence zone which showed maximal effector functions on the cells. The binding of Clq to IgG 2 complexes increased markedly the amounts of complexes bound to the cells, but it reduced O₂^- generation. These results suggest that the difference in abilities of IgG 1 and IgG 2 complexes to promote O₂^- generation may be caused by different structures of the Fe parts or their antigen complexes involved in priming macrophages for O₂^- generation.