NEUTRALIZATION OF BOVINE CONCANAVALIN-A T-CELL SUPERNATANT-MEDIATED ANTI-COWDRIA RUMINANTIUM ACTIVITY WITH ANTIBODIES SPECIFIC TO INTERFERON-GAMMA BUT NOT TO TUMOR-NECROSIS-FACTOR

In an earlier study we demonstrated that Concanavalin-A stimulated bov ine T cell supernatants inhibited the growth of Cowdria ruminantium in bovine endothelial cells in vitro. An investigation was conducted to identify the cytokines which were responsible for this growth inhibiti on. Addition of antiserum against bovine interferon gamma (IFN gamma) reproducibly neutralized the inhibitory effect of the T cell supernata nts, whereas addition of antisera against bovine tumor necrosis factor alpha (TNF alpha) had no effect. The inhibitory effect of IFN gamma o n C. ruminantium growth was not mediated by the production of nitric o xide as there was no; detectable difference in nitric oxide levels in cultures that were supplemented with T cell supernatants compared with those that were not. The IFN gamma mediated anti-C. ruminantium effec t highlights the importance of cell mediated immune responses in contr ol of these infections and in particular incriminates the protective r ole of T cells, or cells that secrete IFN gamma.