Correlation of circulating immune complexes and complement breakdown products with the severity of the disease in human schistosomiasis mansoni.

Circulating immune complexes and complements compounds were measured in serum and plasma from 66 patients with three different clinical forms of chronic schistosomiasis mansoni: intestinal, hepato-intestinal and hepatosplenic. Three different methods were used: the 125I-C1q-binding assay, conglutinin-binding assay (KgB) and Raji cell-binding assay. Approximately 25% of the patients were positive for circulating immune complexes as measured by the C1q and Raji assays. The levels of complexes increased significantly with the severity of the disease. 60% of the patients were positive for immune complexes as measured by the KgB-assay but the incidence of positive results was not clearly influenced by the stage of the disease. There was no significant correlation between immunoglobulin levels and immune complexes. The complement profile of these patients does not suggest a dramatic activation of the complement system. However, there was a progressive decrease in the plasma levels of C4 and an increase of C3d levels which correlated significantly with the severity of the disease.