Autoimmune myocarditis induced by Trypanosoma cruzi.

Antiheart immune reactions have been reported in patients with Chagas' disease, and we have postulated that the observed cardiac lesions are mediated by autoimmune antiheart reactions elicited by the etiologic agent Trypanosoma cruzi. In this report, BALB/c mice infected with a low inoculum of T. cruzi developed splenic lymphocyte cytotoxicity against normal syngeneic neonatal cardiac myofibers in vitro 150 days after infection, whereas splenic lymphocytes obtained from mice at 15, 45, 90, or 120 days after infection or from matched controls did not. No antiheart antibody or antibody-directed cellular cytotoxicity was observed, nor was there an increase in natural killer cell activity. Hearts from mice studied at 150 days after infection showed mononuclear cell myocarditis with myocytolysis in the absence of intracellular T. cruzi forms. Hearts from the other mice did not exhibit any histologic changes. Other reports from our laboratory have identified a cross-reacting antigen (SRA) shared by T. cruzi and striated muscle. Immunization of BALB/c mice with SRA produced immunopathogenic dynamics similar to those seen with long-term T. cruzi infection. Collectively these data indicate that the cardiac lesions seen in patients with Chagas' disease may be attributed to autoimmune reactions elicited by cross-reacting antigens of T. cruzi and striated muscle.