RESUMEN
Studies of interaction between the immune complex [IC] of DNA and anti - DNA antibody and mouse peritoneal macrophages are continued in this report with emphasis upon the effect of serum and various serum components. It was found that 10 human, mouse, and dog sera substantially inhibited the binding of IC. Guinea pig serum had much less of such an inhibitory effect. Heating at 56°C for 30 minutes removed much of the inhibitory effect of the mouse and dog sera but not of the human sera. Deaggregated IgG derived from these animals at the concentration of 1280 .micro g/ml inhibited IC binding by macrophages. The extent of the inhibition of IC by IgG varied with the source of the IgG; mouse IgG as low as 80 microg /ml had inhibitory activity, guinea pig and dog IgG was not inhibitory below 1280 microg/ml. In this assay system, the differences in the inhibition of IC binding in the presence of IgG of various species may indicate the affinity and avidity differences of Fc receptors toward the species IgG