Predominance of CD8⁺ T lymphocytes in the inflammatory lesions of mice with acute Trypanosoma cruzi infection

Using glycol methacrylate in conjunction with avidin-biotin-peroxidase complex techniques, we studied the contribution of T cell subsets to tissue inflammation during acute Trypanosoma cruzi infection. Two mouse/parasite model systems whose parasitology and pathology behaved differently were used. In C57B1/6J mice infected with the T. cruzi Brazil strain, the levels of parasitism in blood and tissue (myocardial and skeletal muscle) reached a maximum at week 6 and decreased rapidly thereafter. Inflammatory responses in tissue corresponded with the parasitism, but decreased in intensity more gradually than that of parasitism. The T lymphocytes (Thy 1.2⁺) were found to be the major lymphocyte population in inflammatory cardiac and skeletal muscles (64.6-81.2%) at both three and six weeks postinfection. Among T cells, CD8⁺ cells (47.0-58.9%) significantly outnumbered CD4⁺ cells (9.3- 18.6%). The number of B cells (0-1.0%) and macrophages was low. Experiments using C3H/HeSnJ mice infected with the Sylvio X10/4 clone of T. cruzi at 30 days postinfection resulted in similar findings except for a higher CD8⁺:CD4⁺ ratio. The primary finding of this study is that Thy 1.2⁺CD8⁺CD4⁺ T lymphocytes are the major cell population in both heart and skeletal muscle in acute murine T. cruzi infection. The predominance of CD8⁺ T cells coincident with the decrease in the tissue parasite burden suggests a role for CD8⁺ T cells in the control of T. cruzi at the level of the infected cell.