Immune depression in trypanosome-infected mice. II. Characterization of the spleen cell types involved.

Spleen cells from Trypanosoma congolense-infected mice showed a drastic depression in their capacity to respond to B and T lymphocyte mitogens and to allogeneic spleen cells in mixed lymphocyte cultures. Spleen cells from infected mice were also poor stimulators in mixed lymphocyte cultures. The poor responsiveness or stimulation capacity was not due simply to dilution of relevant B or T lymphocytes by the large number of null cells found in the spleens of infected animals. These null cells expressed approximately eight times more H-2 antigen than spleen cells from normal (uninfected) mice and were devoid of Ia antigens.