Effect of IgG and C-reactive protein on complement depletion by monosodium urate crystals.

Complement activity in normal human serum was rapidly depleted by the addition of monosodium urate crystals (MSUC), while the same MSUC preparation had little effect on complement activity in 4 of 8 sera from patients with common variable immunodeficiency (CVID). The degree of complement depletion in the CVID sera correlated with their C-reactive protein (CRP) concentrations but not with their concentrations of IgG. MSUC-induced complement depletion in the 4 poorly reactive sera was partially restored by addition of CRP or by normalizing the IgG concentration, but not by addition of IgM or IgA. It is proposed that CRP, an acute phase protein, may play a role in the pathogenesis of gouty arthritis attacks occurring in some patients following surgery or acute physical illness.