Schistosomal egg antigen‐responsive CD8 T‐cell population in Schistosoma mansoni‐infected BALB/c mice

We demonstrated here that schistosomal egg antigen (SEA) is able to stimulate an antigen‐specific, cytotoxic CD8+ T‐cell response in mice. Indeed, a single i.p. immunization with SEA resulted in the in vivo induction of significant cytotoxic T lymphocyte (CTL) activity in the spleen within 20 days. Effector cells were classic class I major histocompatibility complex (MHC)‐restricted CD8+ lymphocytes producing interferon‐γ (IFN‐γ) and interleukin‐2 (IL‐2), suggesting a type 1 response to SEA. We therefore investigated the relevance of these observations in the context of the Schistosoma mansoni parasite infection. CTL activity against SEA‐pulsed target cells was evidenced throughout the infection after in vitro stimulation of recovered splenic cells with SEA demonstrating that SEA‐specific CD8+ T cells with cytotoxic potentialities are present during infection. This activity was strongly increased after immunization of mice with SEA like the production of IFN‐γ in the sera. A marked reduction in the number of granulomas and of fibrosis with the presence of cells producing IFN‐γ in the liver was also observed leading to the survival of SEA‐immunized mice