Mice with a deficiency of IFN-γ or IFN-γ receptor have a higher susceptibility to L. major infection, accompanied by elevated Th2-type responses compared to the wild-type mice, but IFN-γ-deficient mice do not appear to succumb to L. amazonensis until 2 months post infection, suggesting that IFN-γ is induced at different stages of infection by diverse Leishmania species [53,54,81]. This evidence concerns the gene IFNG and infection.