Animals deficient of TRIF and MyD88 infected with T. cruzi are more susceptible to infection, with higher parasitism and low macrophage activation, resulting in a low production of nitric oxide (Campos and Gazzinelli, 2004; Koga et al., 2006; Bafica et al., 2006; Oliveira et al., 2010). This evidence concerns the gene MYD88 and infection.