As seen in BALB/c mice (Fig. 2), the restricted availability of type 1 cytokines early during infection resulted in diminished proportions of Th2/1 cells in blood (Fig. 7a) and in significantly reduced frequencies of IFN-γ producing cells within the parasite-specific CD4+ CD40-L+ populations in spleen and peritoneal cavity (Fig. 7b). This evidence concerns the gene CD4 and infection.