Involvement of suppressor cells induced with membrane fractions of trypanosomes in immunosuppression of trypanosomiasis.

We showed that infection with Trypanosoma congolense in mice led to suppression of listeria-induced delayed type hypersensitivity (DTH). Mice were pre-treated with irradiated T. evansi, which caused rapid and effective suppression of DTH. A membrane fraction obtained by homogenizing T. evansi variant in a hypotonic buffer solution and centrifuging it at 150,000g produced suppression of listeria-induced DTH when injected i.p. into mice as early as 1 day before listeria immunization. Furthermore, we demonstrated by an adoptive transfer system that the suppressor cells involved in this suppression had developed in the spleen and that the activity of the splenic suppressor cells was due to the presence of a macrophage population.