The immunology of experimental Chagas' disease. II. Delayed hypersensitivity to Trypanosoma cruzi antigens.

Homogenates of suspensions of the trypomastigote and amastigote forms of the Ernestina strain of Trypanosoma cruzi, derived from tissue cultures, yielded two subcellular fractions which elicited strong delayed hypersensitivity reactions in rabbits. The 100,000 g times 90 minute fraction of T. cruzi homogenates gave rise to marked cell-mediated immunity. The 30,000 g times 35 minute fraction of these homogenates was also capable of eliciting a marked cell-mediated immune response. Cell-mediated immunity was assayed by experiments which established passive transfer, inhibition of blood mononuclear cell migration and blast transformation by T. cruzi--sensitized lymphocytes. Sensitized lymphocytes did not have observable effects on trypomastigotes of T. cruzi. The results of the experiments described here strongly suggest that constituents of intracytoplasmic particles of trypomastigotes and amastigotes of T. cruzi are involved in eliciting cell-mediated immunity in rabbits.