In a previous work the authors demonstrated that immunization with Schistosoma mansoni 28-kDa glutathione-S-transferase (Sm28GST) was able to reduce hepatic damage in infected mice and that the adoptive transfer of Sm28GST-specific T cells reproduced the protective effect obtained with the recombinant molecule. In the present paper, the authors show that Sm28GST is also able to stimulate an antigen-specific, cytotoxic T-cell response against Sm28GST-pulsed P815 target cells in normal mice and that effector cells induced in vivo were classical Class I MHC-restricted CD8+ lymphocytes. The authors found no spontaneous CTL activity against Sm28GST-pulsed target cells during the course of the infection by S. mansoni although Sm28GST is expressed at different developmental stages of the parasite. It was observed, however, that immunization with Sm28GST is sufficient to elicit a significant level of CTL response for 6 weeks in infected mice. The role of these Class I MHC-restricted CD8+ lymphocytes in the protection observed precisely at the same period in immunized mice remains to be elucidated. The authors also observe that immunization with the lipopeptide form of the C-terminal peptide of the molecule (190-211 peptide) led to a CTL activation comparable to that observed after immunization with the whole molecule demonstrating the feasibility of using a synthetic lipopeptide as immunogen for a CTL response against Sm28GST epitopes. Moreover, like Sm28GST-specific CTLs, 190-211 lipopeptide-specific cells were also Class I MHC-restricted lymphocytes.