In resistant mouse strains, the abundance of Th1 type cytokines; IFN-γ, IL-2, and lymphotoxin spontaneously cleared the L. major infection, whereas, in susceptible mouse strains, infection led to the fatal disease by the action of Th2 type cytokines; IL-4, IL-5 and IL-10 (38). This evidence concerns the gene IFNG and infection.