Trypanosomiasis in mice with naturally occurring immunodeficiencies.

By using mice with naturally occurring defects, we have shown that an intact macrophage system is crucial to survival with the pathogenic protozoan Trypanosoma rhodesiense, since a defect in these cells decreased survival by half. Deficiencies in natural killer cell function or complement levels had no effect on survival. However, the capacity to survive trypanosomiasis was not related to the levels of parasitemia achieved during infection.