CD4 and infection: T cells as well as antibodies are required to control infection.13, 14, 15 CD8 T cells eliminate cells harboring parasites in the cytoplasm, whereas both CD4 and CD8 T cells produce IFN-γ and activate macrophages to restrain infection.16, 17 Effector T-lymphocytes also promote immunopathology in the heart.18, 19 Conversely, regulatory mechanisms, provided by cytokines and apoptosis of effector cells, dampen inflammation and prevent pathology, but might contribute for parasite persistence.20, 21