ABSTRACT
Gamma interferon (IFN-gamma) plays an important role in experimental Trypanosoma cruzi infections, presumably by controlling the early replication of parasites in host macrophages. In this work, we show that NK cells represent an important cell type responsible for the production of most of the IFN-gamma in the early stage of T. cruzi infection and that the in vivo treatment of mice with anti-NK1.1 monoclonal antibody made resistant animals susceptible to the infection. Through in vitro experiments, we demonstrate that normal splenocytes from euthymic or athymic nude mice cultivated for 48 h with live T. cruzi trypomastigotes produced elevated levels of IFN-gamma. In addition, NK-depleted splenocytes show a drastic reduction of IFN-gamma production in response to live T. cruzi trypomastigotes. We also demonstrated that IFN-gamma production is dependent on a factor secreted by adherent cells. Supernatants of spleen cells from athymic nude mice are able to induce IFN-gamma production by normal splenocytes when cultured with trypomastigotes. The addition of anti-interleukin-10 to these cultures resulted in a marked increase in IFN-gamma production. On the other hand, the absence of NK cells led to an increased secretion of interleukin-10 upon in vitro stimulation with T. cruzi. Taken together, these results suggest that NK cells are the major source of IFN-gamma that could be involved in limiting the replication of T. cruzi in host macrophages during the early acute phase of the infection.
