Abstract
In the study reported here, we used RT-PCR with primers specific for interleukin-1 (IL-1), IL-6, IL-10, tumor necrosis factor-α (TNF-α), and nitric oxide synthase (iNOS) to assess the cytokine mRNA expression associated with bovine blood monocytes during their differentiation to macrophages cultured on plastic (1 week). In addition, we used RT-PCR to assess the contribution of γδ T cells as a source of interferon-γ (IFN-γ), the induction signal for iNOS. Further, we evaluated cytocentrifuge preparations from the cultures for the production of IL-10 using specific antibody. We previously demonstrated that iNOS can be induced in cultured bovine monocytes in response to IFN-γ and TNF-α but lose this capability in a short period of time. However, we demonstrate here that iNOS induction from monocytes cultured with IFN-γ secreting γδ T cells is prolonged, suggesting that this source of IFN-γ primes the monocytes before exogenous stimulation. Based on mRNA expression, placement of monocytes in culture resulted in activation, followed by quiescence. By 6 days in culture, the iNOS message was reduced below the basal level. In addition, the TNF-α message was substantially reduced, and IL-1 and IL-6 messages were reduced below detectable levels. This correlated with an increase in IL-10 message. Downregulation of these same cytokine messages as well as IFN-γ message occurred within a 20-h period when IL-10 was added exogenously to cultures of total leukocytes. At the same time, there was an increase in the number of IL-10-positive cells and an increase in the intensity of anti-IL-10 staining within adherent cells. These results provide evidence for IL-10 regulation of some bovine mononuclear phagocyte effector functions.
Get full access to this article
View all access options for this article.