Chronic serum sickness glomerulonephritis: removal of glomerular antigen and electron-dense deposits is largely dependent on plasma complement.

Chronic serum sickness glomerulonephritis was induced in 20 rats, using radio-labelled cationised bovine serum albumin (BSA) as antigen. Four days after the last dose of antigen, half the rats were given cobra venom factor (CVF) in doses sufficient to render plasma complement activity undetectable. After ten days without circulating complement, the rats had significantly more antigen in glomeruli than the control group. Subepithelial and mesangial electron dense deposits are found in this model: morphometric analysis indicated that the elimination of plasma complement had slowed the removal of deposits at both of these sites. A second experiment studied the kinetics of this effect. CVF was again given four days after the last dose of antigen, but rats were killed in small groups at intervals thereafter. The results indicate that initially decomplementation had little effect, but after seven days without complement the removal of glomerular antigen had virtually ceased. The complement depleted rats had significantly lower levels of proteinuria, despite having more antigen and larger deposits in their glomeruli. In this model therefore, complement appears to be essential for the removal of deposits, and simultaneously contributes significantly to the induction of proteinuria.