Experimental studies have shown that protection against leishmaniasis is mediated by T helper 1 (Th1) type CD4+ cells that produce a high level of interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α) whereas progression of the disease is associated with Th2 type CD4+ cells which produce IL-4, IL-5, IL-10, and IL-13 [6–9]. Here, IFNG is linked to leishmaniasis.