Circulating immune complexes and C3d in human parasitosis

The occurrence of glomerulonephritis in schistosomiasis has been documented over the past 10 years [1–4]. The presence of granular deposits of immunoglobulin and complement in the glomeruli suggests that they may be secondary to immune complexes (IC). The formation of IC in the blood can be expected from the simultaneous occurrence in the circulation of parasitic antigens and the corresponding antibodies. A limited number of studies devoted either to human or experimental situations have shown the presence of material behaving as IC in helminthic infections, in some cases by radiolabeled Clq assay, and in others by inhibition of EAC rosette formation [5–7]. In a few patients, indirect evidence has been provided suggesting that schistosomial antigens were present in the IC [7, 8]. In the present study, we have tested the sera of patients suffering from various parasitosis with the sensitive Raji cell radioimmune assay [9]. We chose this method because the immune complex bound to the Raji cell surface is directly accessible to identification of the antigenic moiety. Furthermore, the patients were clinically studied carefully for the presence of nephritis, and biologic evidence of complement activation