CD4 and infection: To establish the specific source of IFN-γ responsible for the observed initial control of parasite load at the site of infection, we transferred sorted effector CD4+ or CD8+ T cells from T. cruzi-infected wild-type or IFN-γ knockout (KO) mice into IFN-γ-deficient C57BL/6 mice prior to infection with tdTomato-expressing T. cruzi.