The role of cytokines in the pathogenesis of hepatic granulomatous disease in Schistosoma mansoni infected mice.

Cytokines are important in the cell-mediated response to Schistosoma mansoni eggs. We have found that Th2 cytokine responses (e.g. IL-4 and IL-5) are augmented after egg laying begins while Th1 responses (IL-2 and IFN-gamma) are down regulated in S. mansoni infected mice. Treatment of mice with anti-IL-5 monoclonal antibodies (Mab) suppressed the eosinophil response almost completely but did not affect granuloma size and slightly increased hepatic fibrosis. Anti-IL-4 treatment abolished IgE responses in infected mice and decreased hepatic fibrosis slightly. Anti-IFN-gamma treatment had no effect on hepatic pathology. Anti-IL-2 treatment decreased granuloma size significantly and decreased hepatic fibrosis markedly. Anti-IL-2 treatment dramatically decreased IL-5 secretion by splenic cells in vitro and decreased peripheral blood and tissue eosinophilia. In contrast IL-4 secretion was unaffected and serum IgE was normal or increased. IL-2 and IFN-gamma secretion by splenic cells of treated mice were slightly but not significantly increased suggesting that anti-IL-2 treatment is affecting Th2 rather than Th1 responses.