A comparative study of complement components in polyethylene glycol precipitated immune complexes from patients with ovarian cancer and patients with rheumatoid arthritis.

Circulating immune complexes and complement components C1q, C3 and C4 were measured following polyethylene glycol precipitation of serum from patients with ovarian cancer (OC), patients with rheumatoid arthritis (RA) and control patients (CP). The C3 and C4 content of the precipitated material was significantly greater in those patients with OC in comparison to those with RA or CP, while the C1q content did not differ significantly between the two groups of patients. A statistically significant correlation between IgG, C3 and C4 levels was found in the immune complexes of both groups of patients. C1q levels correlated significantly with IgG immune complex levels in patients with RA and CP, but did not in patients with OC. These data illustrate that immune complexes from patients with OC differ from complexes precipitated from RA sera and normal sera in their complement content. It is suggested that the largely unsuccessful attempts to detect immune complexes in sera from patients with ovarian cancer, using assays dependent on the binding of C1q may be related to differences in solubility of complexes from these patients in comparison to complexes present in non-neoplastic conditions.