Thymus-dependent control of host defense mechanisms against Trypanosoma cruzi infection.

Congenitally athymic homozygous (nu/nu) mice were shown to be significantly more susceptible to Trypanosoma cruzi infection than their thymus-bearing heterozygous (nu/+) littermates, as measured by increased parasitemia, mortality rate, and shortened survival time. In addition, transplantation of neonatal thymus into athymic mice reestablished normal levels of resistance to T. cruzi, i.e., comparable to those of normal littermates. These results constitute conclusive evidence that host defense mechanisms active in experimental Chagas' disease are under thymic control.