Immune depression in trypanosome-infected mice. I. Depressed T lymphocyte responses

Using a wide range of experimental conditions, several kinds of T lymphocyte responses in spleen cell populations from trypanosome‐infected mice were studied. Lymphocyte stimulation after culture with the mitogen concanavalin A or with histoincompatible cells differing at H‐2 or minor lymphocyte‐stimulating loci was reduced or abolished in spleen cells from infected mice when compared with responses of spleen cells from uninfected controls. In addition, cytotoxic lymphocytes were not generated in mixed lymphocyte cultures which contained spleen cells from infected animals. Allogeneic skin grafting experiments performed with normal and infected mice showed that a decreased T lymphocyte response also occurs in vivo. The depressed immune responses were not simply due to low numbers of T lymphocytes in spleens of infected animals, but reflected a generalized immune depression which was not antigen‐specific.