Autoimmunity in Chagas' disease: specific inhibition of reactivity of CD4+ T cells against myosin in mice chronically infected with Trypanosoma cruzi.

In this study, we assessed the proliferative response of T cells from mice chronically infected with Trypanosoma cruzi to actin, myosin, or T. cruzi soluble antigen (SA). We report here that CD4+ T cells from mice chronically infected with T. cruzi proliferated in response to myosin but not to actin, whereas cells from naive mice did not proliferate against any of the antigens tested. Antisera raised against myosin- or SA-activated T cells specifically inhibited respectively, the myosin or SA in vitro proliferative response, whereas the response to unrelated antigen remained unimpaired. Sera from chronically infected mice failed to show any significant inhibitory activity. The above findings suggest that autoreactive and T. cruzi-reactive T cells belong to different, perhaps nonoverlapping, compartments of the immune cell repertoire of mice chronically infected with T. cruzi. The failure of infected mice to trigger the suppressive mechanisms described here might be the primary immune defect leading to breakdown of self-tolerance and unopposed, perhaps tissue-damaging, autoimmunity in experimental Chagas' disease.