Immunopathology of Schistosoma mansoni infection.

Schistosomiasis mansoni is a chronic helminthic disease that affects about 100 million people in the tropics. The worms have a life span of 5 to 10 years, and they live in the mesenteric veins of the host. Lightly infected individuals are asymptomatic or manifest mild intestinal symptoms. Heavily infected individuals often develop severe morbidity with hepatosplenomegaly, sometimes with a fatal outcome. Morbidity is attributed to the strong humoral and T-cell-mediated host immune responses developed to a variety of parasite antigens and expressed as tissue inflammations. The immunopathology includes dermatitis, immune complex-mediated kidney disease, and, chiefly, T-cell-mediated granuloma formation and fibrosis around disseminated parasite eggs. This review describes the mechanisms of induction and expression of immunopathology in infected persons and experimental animals. Immunoregulatory mechanisms that modulate the enhanced immune responses and may ameliorate excessive morbidity are discussed.