Effects of extracts of Trypanosoma cruzi on immune responses: induction of a nonspecific suppressor factor.

Extracts of epimastigotes of Trypanosoma cruzi were examined for the ability to augment or suppress in vivo and in vitro responses of mouse spleen cells. When administered to mice 4 days before immunization with sheep erythrocytes, the 12,000 X g pellet and the 104,000 X g pellet and supernatant fractions of extracts of T. cruzi had no effect on the subsequent plaque-forming cell responses. Testing of the two 104,000 X g fraction in vitro resulted in a slight dose-dependent modification of anti-sheep erythrocyte responses. Also, these two fractions had a moderate dose-dependent blastogenic effect on normal spleen cells. Most significantly, the 104,000 X g supernatant fraction elicited the production of a suppressor factor when incubated with spleen cells from infected mice. This suppressor factor was also apparent when spleen cells from infected mice were incubated with intact epimastigotes or trypomastigotes. Production of the suppressor factor was insensitive to indomethacin and, therefore, presumably was not a prostaglandin.