Tumour necrosis factor (cachectin) production during experimental Chagas' disease.

Mice infected with the protozoan parasite Trypanosoma cruzi are primed for the production of tumour necrosis factor/cachectin. Active infection is not required for stimulation of TNF production as formalin-fixed, but not heat-killed, parasites can act as a priming stimulus. Both epimastigote and trypomastigote stages of the parasite can prime for TNF production but on a per cell basis, trypomastigotes are more potent stimulators than epimastigotes and live parasites prime more efficiently than killed preparations. Although the priming effect of epimastigotes and trypomastigotes is dose-dependent when assayed 10 days after parasite injection, parasitemia levels in the infected mice do not correlate with the level of TNF production. Spleen cells from infected mice are also primed for the production in vitro of TNF in response to LPS or T. cruzi. These results suggest that TNF may be constitutively produced in vivo and that the priming for TNF production, or the production itself, may be regulated during the course of the infection in mice.