Trypanosoma cruzi: the T-cell dependence of the primary immune response and the effects of depletion of T cells and Ig-bearing cells on immunological memory

The effects of T-cell depletion on primary infection with Trypanosoma cruzi and on immunological memory to this parasite were studied in a syngeneic mouse system. Exacerbation of T. cruzi infections occurred in thymectomized, irradiated, bone marrow-reconstituted (TX) C57BL/6J mice compared to sham thymectomized, irradiated, bone marrow-reconstituted (STX) mice. Reconstitution of TX mice with thymocytes restored the resistance to a level equivalent to that of STX mice. Immunological memory against T. cruzi present in spleen cells in mice recovered from T. cruzi infections could be ablated by treatment with rabbit anti-brain-associated theta serum but not with rabbit anti-mouse immunoglobulin serum prior to adoptive transfer of immune spleen cells into TX mice. These experiments suggest that modulation of the primary immune response and memory against T. cruzi depends largely on the thymus-derived lymphocyte. The possible implications of this T-cell regulation on previously reported effector mechanisms againt this parasite are discussed.