Complement components and immunoglobulins in patients with schistosomiasis.

Serum C3 levels in Egyptian adult males with chronic and repeated schistosomiasis (haematobium or mansoni) were lower in those with circulating schistosomal antigen, with or without antibody, than in those with circulating antibody alone. The sera were anticomplementary more frequently in those with antigen and antibody than in the other groups. C3 and C4 were low in anticomplementary sera of any group, suggesting complement activation by the classical pathway. Serum IgG and IgM were higher in the patients than in the controls, but IgA was lower. In patients with circulating antibody, IgM was higher in those with S. mansoni than in those with S. haematobium. IgE was very high in all the patients, but higher in those with anticomplementary sera than in those without. No patient had more than minor proteinuria. The implications of these relationships for the immunopathological effects of schistosomiasis and for the heterogeneity of antigen clearance are discussed.