IL-12 enhances proliferation of peripheral blood mononuclear cells from Chagas' disease patients to Trypanosoma cruzi antigen

Chagas' disease is caused by infection with Trypanosoma cruzi. Patients in the chronic phase of infection were grouped as belonging to the asymptomatic (or indeterminate), cardiac and cardiac plus digestive forms. Previous studies have described abnormal immune responsiveness by peripheral blood mononuclear cells (PBMC) from chronic chagasic patients. We report significant parasite antigen (T-Ag)-stimulated PBMC proliferative responses to be present in all three groups of patients. Treatment of T-Ag-stimulated cultures with rIL-12 significantly amplifies proliferative responses in all patients' groups, with similar rates of increment. IL-12 enhances T-Ag-specific lymphoproliferation without increasing proliferation of unstimulated PBMC from normal individuals or from patients. Comparatively, treatment with rIL-2 enhances both T-Ag-specific and unstimulated proliferation by PBMC from patients and normals. Thus, IL-12 acts on pre-activated cells while IL-2 also stimulates resting cells. No synergism was obtained by the combined use of IL-12 and IL-2. Therefore IL-12 can act as a more selective amplifier of T. cruzi reactive cells than IL-2. IL-12, by enhancing parasite-antigen specific immunity, could be of potential therapeutic use to control reactivated T. cruzi infections concomitant to AIDS or other situations of immunosuppression.