During the chronic phase, a coexistence of the Th1 (IL-12, IFN-γ, and TNF) and Th2 profiles (IL-4 and IL-10) may be observed, and the equilibrium between these profiles may be relevant to disease morbidity [3, 14, 15]; that is, a Th1 response aggravates and a Th2 response produces a better outcome in murine trypanosomiasis and human Chagas disease [16–20]. The gene discussed is IL10; the disease is Chagas disease.