Defective C3b receptor-mediated phagocytosis of neutrophils in patients with primary biliary cirrhosis

Abstract

Neutrophil function in patients with primary biliary cirrhosis (PBC) was studied by means of a kinetic particle uptake assay using IgG-coated and IgG + C3b-coated latex particles, enabling a differentiation between Fc and C3b receptor-mediated phagocytosis. C3b receptor-dependent phagocytic rate (delta C3b) in PBC was significantly decreased (PBC = 0.20, 0.08-0.51 min-1; reference = 0.37, 0.23-0.60 min-1; p less than 0.0005 (-x; +/- SD logarithmically transformed], whereas the Fc receptor-dependent phagocytic rate was normal. delta C3b was inversely correlated with complement factor C3 levels (r = -0.77, p less than 0.02) and C3b receptor-binding activity (r = 0.47, p less than 0.04) in PBC sera, indicating a possible relationship between serum components and neutrophil C3b receptor dysfunction. These observations are in accordance with previously reported defects of C3b receptor function in monocytes and lymphocytes, suggesting a generalized disturbance of C3b receptor-bearing cells in PBC. Furthermore, the effect of PBC sera on migratory function of normal neutrophils was investigated. PBC sera contained heat-labile, chemokinetic stimulating activity. The mean chemotactic activity of PBC sera did not differ from that of reference sera.