Resistance to American cutaneous leishmaniasis is related to the emergence of responses with the participation of CD4+ T cells with a Th1 profile, with the production of pro-inflammatory cytokines such as IL-1, IL-2, IL-12, IFN-γ, and TNF-α, which lead to macrophage activation and parasite death. The gene discussed is TNF; the disease is cutaneous leishmaniasis.