Given that both Il18r1−/− and Myd88−/− infected mice displayed lower levels of Th1 cells in the spleen, when compared to WT animals, we asked whether the adoptive transfer of WT CD4+ T lymphocytes to Il18r1−/− and Myd88−/− strains would be enough for lowering parasitemia levels and improve survival to infection, in accord with the crucial role of Th1 responses for protection against T. cruzi infection (Michailowsky et al., 2001). This evidence concerns the gene IL18R1 and infection.