Inhibition of immune complex solubilization by sera of patients with membranoproliferative glomerulonephritis.

Inhibition of complement mediated solubilization (CMS) of preformed immune complexes was previously demonstrated in the serum of patients with systemic lupus erythematosus. We studied the ability of serum from patients with MPGN I or III to inhibit the solubilization of preformed BSA- anti-BSA aggregates by pooled normal human serum. Inhibition of CMS was found in the sera of 20/35 patients; the inhibition was more dramatic in those with active disease (9/9), as compared to those in remission (8/21) or with renal failure (3/5). The inhibition did not seem to be related to corticosteroid therapy, nephrotic syndrome, circulating immune complexes or hypocomplementaemia. In only one patient was inhibition associated with the presence of C3 nephritic factor activity and decomplementation of the target serum.