“…There is accumulating evidence that a steady balance between host and parasite is usually present in Chagas' disease and that cellular immunity is important in this balance: parasitemia is very low, and it is remarkably difficult to find parasites at the sites of the lesions (4); outbreaks of high parasitemia can be obtained only by using strong immunosuppressive agents (1,18); experimental, acute Chagas' disease is easily induced after neonatal thymectomy or treatment with antithymocyte serum (17,20); and immunity is achieved by lymphocyte transfer (7,16,18). On the other hand, the presence in the heart of mononuclear cell infiltrates suggests the possible participation of immune mechanisms, especially autoimmune and delayed hypersensitivity reactions, in the pathogenesis of the chagasic cardiopathy (14). In keeping with these concepts, Santos-Buch and Teixeira (19) have recently reported in vitro lysis of allogeneic, parasitized, and nonparasitized heart cells by T. cruzi-sensitized rabbit lymphocytes.…”