Studies have signified that a set of cytokines are respectively involved in the leishmaniasis progression, and host protection entails cytokines, including TGF-β and interleukins (IL)-4, IL-5, IL-6, IL-9, IL-10, IL-27, and IL-33 and also inducible nitric oxide synthase (iNOS), interferon (IFN)-γ, tumor necrosis factor-α, IL-2, IL-7, IL-8, IL-12p40, IL-15, IL-22, and IL-23. The gene discussed is NOS2; the disease is leishmaniasis.