High and low responsiveness of bovine lymphocytes to Trypanosoma brucei in vitro: lack of correlation with resistance to trypanosomiasis.
Bovine peripheral blood lymphocytes (PBL) were stimulated to proliferate in vitro by live, irradiated or freeze-thawed Trypanosoma brucei, but not by the isolated variant surface glycoprotein. The optimal dose was 10(5) trypanosomes per 5 X 10(5) lymphocytes in 0.2 ml. Maximal proliferation was at day 5. Of the 98 cattle tested, 36 were high-responders (stimulation indexes 20-104), 49 were low or non-responders (SI 1-10) and 13 were intermediate. The responder status of individual animals did not change over a period of 1 year, nor did it alter following deliberate trypanosome infection. The stimulation was dependent on macrophage/monocyte type accessory cells, and this co-operation did not seem to be MHC restricted. Lack of stimulation of non-responder PBL did not appear to be due to the activation of suppressor cells. Accessory cells from non-responder animals could complement PBL from responders, but accessory cells from responders could not complement non-responder PBL. Responsiveness is therefore a characteristic of lymphocytes. Analysis of the surface markers of these lymphocytes or the blast cells generated in culture showed that they were a subpopulation of T cells, possibly TH cells. Analysis of PBL from 98 animals, which had been selected for trypanoresistance or trypanosensitivity under natural tsetse fly challenge, failed to establish a correlation between resistance and level of lymphocyte stimulation by trypanosomes in vitro.
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D000953:Antigens, Protozoan / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology; D002417:Cattle; D004306:Dose-Response Relationship, Immunologic; D007113:Immunity, Innate; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D013601:T-Lymphocytes / Q000276:immunology; D013997:Time Factors; D014346:Trypanosoma brucei brucei / Q000276:immunology*; D014354:Trypanosomiasis, Bovine / Q000276:immunology*
D000953:Antigens, Protozoan; D000954:Antigens, Surface