Immune-complex inhibition of macrophage activation is not due to an interaction with the binding or processing of IFN-gamma.

Preincubation of macrophages with immune complexes suppresses the interferon-gamma (IFN-gamma) induction of tumouricidal activity and Ia surface expression. The studies reported in this manuscript were designed to test if immune complexes alter the interaction of IFN-gamma with macrophages. The binding of IFN-gamma to its specific cellular receptor, the uptake or the degradation were not affected by preincubation of macrophages with immune complexes. Preincubation of macrophages with high doses of phorbol esters mimics the inhibitory effect of immune complexes. This suggests that a strong activation of protein kinase C suppresses a subsequent activation of macrophages by IFN-gamma.