Defective C3b Receptor-Mediated Phagocytosis of Neutrophils in Patients with Primary Biliary Cirrhosis

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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 (AC3b) in PBC was significantly decreased (PBC = 0.20, 0.084.51 min−1 reference = 0.37, 0.23–0.60 min-1; p < 0.0005 (x¯ ± SD logarithmically transformed), whereas the Fc receptor-dependent phagocytic rate was normal. AC3b was inversely correlated with complement factor C3 levels (r = −0.77, p < 0.02) and C3b receptor-binding activity (r = −0.47, p < 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.