Use of parasite antigens and interleukin-2 to enhance suppressed immune responses during Trypanosoma cruzi infection in mice.

Mice infected with Trypanosoma cruzi exhibit an early and profound suppression of parasite-specific and nonspecific immune responses. Earlier studies have shown that this suppression is due, at least in part, to suppressor macrophages, deficiency in production of interleukin-2 (IL-2), and reduced T helper (Th)-cell activity. In the present study, the effect of exogenously supplied IL-2 on enhancement of parasite-specific Th-cell activity, anti-parasite immunoglobulin G (IgG) and IgM antibody levels, parasitemia, and longevity was examined in infected mice. The results showed that administration of IL-2 with and without antigenic stimulation with trinitrophenylated T. cruzi significantly enhanced parasite-specific IgM and IgG levels. Injection of IL-2 and trinitrophenylated T. cruzi together significantly enhanced parasite-specific Th-cell activity and was more effective in enhancement of parasite-specific antibody levels. In addition, it was found that IL-2 alone had a rapid and lasting effect in reducing parasitemia. These results suggest that deficiency in IL-2 may play a major role in host susceptibility to T. cruzi.