The delayed onset of death observed in rGRA2 and rGRA5-immunized mice might be due to the interplay between Th1 and Th2-driven responses as findings have shown that Th1-related cytokine primarily IFN-γ causes early mortality whereas Th2-related IL-4 and IL-10 diminish short-term fatality by down regulating Th1 response and thus reducing the severe inflammatory effect provoked by IFN-γ at the early acute phase of toxoplasmosis (Roberts et al., 1996; Neyer et al., 1997; Petersen et al., 1998). This evidence concerns the gene IL10 and toxoplasmosis.