Analysis of B cell and T cell proliferative responses induced by monomorphic and pleomorphic Trypanosoma brucei parasites in mice.

Cells collected from C57B1/6 mice infected with monomorphic and pleomorphic clones of Trypanosoma brucei parasites (ILTat 1.4 and GUTat 3.1) were analysed for the incorporation of 125I-Iododeoxyuridine into DNA of total splenic lymphocytes and of B and T lymphocytes isolated on a fluorescence activated cell sorter. The monomorphic T. brucei ILTat 1.4 parasites triggered delayed and low splenic DNA synthetic responses in comparison to those arising in mice infected with the pleomorphic T. brucei GUTat 3.1 organisms. Mice infected with both parasite clones mounted splenic DNA synthetic responses similar to those arising in animals infected with the pleomorphic organisms alone and similar responses were induced by lethally irradiated T. bruceiGUTat 3.1 and T. brucei ILTat 1.4 parasites. In mice infected with the pleomorphic parasites, DNA synthesis was first detected in the T cell population and B cell DNA synthetic responses were detected between 1 and 2 days later. In contrast only T cell DNA synthetic responses were detected after infection with the monomorphic T. brucei ILTat 1.4 parasites. It is suggested that the previously reported failure of monomorphic T. brucei parasites to trigger antibody production in infected mice is a result of their inability to stimulate B lymphocytes.