HIGH AND LOW RESPONSIVENESS OF BOVINE LYMPHOCYTES TO TRYPANOSOMA-BRUCEI INVITRO - LACK OF CORRELATION WITH RESISTANCE TO TRYPANOSOMIASIS

  • 1 January 1985
    • journal article
    • research article
    • Vol. 54  (1) , 195-203
Abstract
Bovine peripheral blood lymphocytes (PBL) were stimulated to proliferate in vitro by live, irradiated or freeze-thawed T. brucei, but not by the isolated variant surface glycoprotein. The optimal dose was 105 trypanosomes per 5 .times. 105 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 yr, 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 [major histocompatibility complex] 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.