Decreased activity of complement-mediated immune complex clearance in hemodialysis patients

Complement-mediated immune complex (IC) clearance was examined in the sera from regular hemodialysis patients, who accumulated excess factor D in the circulation. Both complement activities for the inhibition of insoluble IC formation and the solubilization of insoluble IC were lower in the sera from these patients than in the sera from normal individuals. A similar decrease in complement activities was observed in normal serum fortified with excess factor D. In addition, complement-processed IC was found to be bound less effectively to human erythrocytes via complement receptor type 1 in the sera from these patients and from normal serum fortified with excess factor D than in normal serum. Gel-filtration HPLC analysis revealed a decrease in covalent binding of C3 fragments to IC solubilized in the sera from hemodialysis patients or in normal serum fortified with excess factor D. This supports the notion that lower complement-mediated IC clearance is due to the paucity of complement fragments bound to IC. It is suggested that some detrimental alterations in the complement system, probably due to excess factor D, cause decreased IC clearance activity in hemodialysis patients with chronic renal failure.