Induction of parasite-specific helper T lymphocytes during Trypanosoma cruzi infections in mice.

Development of parasite-specific T helper cells was examined in mice infected with Trypanosoma cruzi. At various times during the course of infection mice were challenged with TNP conjugated to fixed culture forms of T. cruzi (TNP-TC), and the resultant splenic plaque-forming cells (PFC) against TNP were determined. By day 10 post-infection significant responses against TNP-TC were observed but not against TNP-BSA. Infected mice that were not challenged with TNP-TC did not produce anti-TNP PFC, which demonstrated that the TNP-TC response was not the result of nonspecific B cell activation. Treatment of spleen cells from infected mice with anti-theta antiserum plus C ablated the anti-TNP-TC response when these cells were transferred to normal mice that were subsequently challenged with TNP-TC, whereas treatment of the cells with anti-Ig plus C prior to transfer had no effect on the TNP-TC response. These results demonstrate enhancement of parasite-specific Th activity of mice infected with T. cruzi and that cell-cell interaction in development of responses to neoantigens is fully functional when sensitized Th are present, even though the animals are unresponsive to heterologous antigens.