Neutrophil phagocytosis in sarcoidosis. Reduced C3b receptor-mediated phagocytosis in active and silent sarcoidosis.

The phagocytic and complement receptor function of polymorphonuclear neutrophils (PMN) from patients with sarcoidosis was studied using a kinetic assay which allows the distinction to be made between Fc receptor-mediated and C3b receptor-mediated particle uptake. The study included one group (A) of patients with active disease (n = 20), and one group (B) with silent or inactive disease who since 10 years had no symptoms or radiological signs of sarcoidosis (n = 11). Abnormal C3b receptor function was observed in both groups but the impairment was most pronounced in the A group. The presence of C3b receptor dysfunction in both groups with a quantitative difference between the groups, is compatible with C3b receptor dysfunction being a primary causal factor of sarcoidosis.