The pathological effects of immunosuppression of Schistosoma mansoni-infected mice, with particular reference to survival and hepatotoxicity after thymectomy and treatment with antithymocyte serum, and treatment with hydrocortisone acetate.

The effects of various immunosuppressive regimes on the survival and liver pathology of mice infected with Schistosoma mansoni were investigated. T-cell deprivation before infection (by adult thymectomy and subsequent anti-thymocyte serum administration), or treatment with hydrocortisone or cyclophosphamide or azathioprine after infection, all reduced survival of infected mice when compared with immunologically intact, infected mice. T-cell deprivation or steroids produced severe liver damage in infected mice despite a reduction in the size of the peri-oval granulomatous inflammatory reaction. Administration of chronic infection serum reduced liver damage in both T-cell-deprived and steroid-treated animals, but improved survival only in the deprived animals and not to the level seen in normal infected mice. The liver damage in immunosuppressed mice was not due to opportunistic bacterial infection. Thus, although immunosuppression reduced the granulomatous response to schistosome eggs in the livers of infected mice (as it does to eggs injected intravenously into the lungs), survival time was decreased. The relevance of these findings to human S. mansoni infections is discussed.