Effect of immune complexes on human neutrophil phagocytic function

Phagocytosis by human polymorphonuclear leukocytes (PMN) was quantified with immune complexes containing super(125)l-labeled human serum albumin (HSA) and rabbit IgG antibodies against HSA. By varying the antigen to antibody ratio, immune complexes were obtained that ranged from immune precipitates to soluble complexes. Direct uptake of complexes by PMN was closely dependent on the percent precipitation of the complexes. Preincubation of PMN with immune complexes led to an inhibition of the subsequent ingestion of insoluble immune complexes. The results suggest that prolonged contact of PMN with soluble immune complexes or aggregated IgG leads to reduced phagocytic capacity of the cells through a process that involves metabolic activation of the cells and may be accompained by the loss or denaturation of surface (IgG)Fc receptors.