Immune depression in trypanosome-infected mice. IV. Kinetics of suppression and alleviation by the trypanocidal drug Berenil.

Mice infected with T. congolense were monitored for numbers of parasites in peripheral blood, changes in spleen cell populations, immune depression and suppressor cell activity. Depression of B and T lymphocyte responses and the appearance of suppressor cell activity in spleens of infected mice paralleled the appearance of parasites in the peripheral blood. The immune depression was manifest before any visible changes in spleen cell populations occurred. Treatment of infected mice with the trypanocidal drug Berenil resulted in a rapid clearance of parasites from the peripheral blood, a parallel loss of immune depression and suppressor cell activity and a gradual return towards normal spleen cell composition. The splenic white pulp showed severe depletion following longstanding infection with T. congolense. However, following treatment with Berenil there was rapid repopulation of the white pulp and widespread active germinal centre formation.