Murine T lymphocyte specificity for African trypanosomes. I. Induction of a T lymphocyte-dependent proliferative response to Trypanosoma brucei.

A procedure which results in the specific activation of primed murine T lymphocytes was adapted for the study of T lymphocyte activation by the African trypanosome: Trypanosoma brucei. The assay calls for the in vivo priming of lymphocytes by the subcutaneous administration of parasites, followed by the co-cultivation in vitro of cells taken from the regional draining lymph nodes and the parasite. This co-cultivation results in a marked proliferation of lymphoid cells. The proliferation was shown to be specific for the parasite, and to be dependent on the presence of T lymphocytes and macrophages. Both the in vivo priming and the in vitro activation were shown to require the presence of living parasites. Various factors influencing the magnitude of the proliferative response were analysed. Of special interest is the observation that the time interval between in vivo priming and in vitro culture which results in a substantial proliferative response is quite short when compared to that seen with other antigens. Although lymph node cells from mice primed with T. brucei 1 to 2 weeks previously are able to mount a secondary proliferative response upon stimulation with T. brucei, cells taken 3 weeks after priming are unresponsive to an in vitro challenge with T. brucei. This unresponsiveness may be a result of the generalized immunosuppression seen in African trypanosomiasis. Thus, this method offers the potential for the study of specific T cell responsiveness in African trypanosome infections.