Key features of the immunity in the Chagas disease include (i) predominance of partially activated T CD8 lymphocytes in cardiac inflammatory infiltrates [5], accompanied by high production of nitric oxide (NO), IL-12, monocyte chemoattractant protein-1 (MCP-1), and IFN-γ by infiltrating macrophages; (ii) preponderant IFN-γ production by cytolytic natural killer (NK) cells in the acute phase of the disease to control tissue and systemic parasite burden; and (iii) polyclonal B lymphocyte response [6–13]. This evidence concerns the gene IFNG and Chagas disease.