These infections have an opposite protection immune response, where toxoplasmosis majority elicits a Th1 cellular immunity, which induces the production of IL-12, IL-2, IFN-α and TFN-α cytokines; while individuals with the most severe form of leprosy (lepromatous) generally develop humoral immune response (Th2 type) with production of IL-4, IL-5, IL-10 and IL-13, which suppress macrophage activities and stimulate mast cell and B lymphocyte activation. The gene discussed is IL4; the disease is leprosy.