Trypanosomiasis leads to extensive proliferation of B, T and null cells in spleen and bone marrow.

Changes in the distribution of T, B and null cells in the spleen and bone marrow have been studied in inbred mice infected with . Immunofluorescent staining combined with a H-thymidine pulse and autoradiography showed activation of all three cell types. A transient increase in splenic T cells was followed by dramatic increases in B cells (2·5-fold) and in null cells (35-fold). By day 12, after the first peak of parasitaemia, nearly half the spleen cells were dividing. In the bone marrow, very large blast cells appeared within a week of infection.