Goat γδ T cell subpopulations defined by WC1 expression, responses to pathogens and cytokine production

The major functions of gamma delta T cells in mammals overlap with those of alpha beta T cells but differ in that gamma delta T cells are rapid responders and see different types of antigens. While gamma delta T cells have been shown to be a major population of circulating lymphocytes in artiodactyl species such as cattle, sheep, and pigs, less is known about these cells in goats, an important agricultural species. We have recently shown that WC1, a gamma delta T cell-specific family of hybrid pattern recognition receptors/co-receptors, is a multigenic family in goats expanded beyond what occurs in cattle. This study was conducted to address some of the limitations of previous studies in determining the proportions of gamma delta T cells, WC1(+) gamma delta T cells as well as the WC1.1(+) and WC1.2(+) subpopulations in blood and to evaluate their responses to various pathogens. Previously, the proportion of caprine gamma delta T cells was determined using a monoclonal antibody (mAb) 86D that we show here does not react with all gamma delta T cells thereby underestimating their contribution to the lymphocyte population. Using a mAb reactive with the TCR delta constant region we found the proportion of gamma delta T cells in blood was not significantly less than that of either CD4 or CD delta T cells and did not decrease with age after 6 months. gamma delta T cells that expressed WC1 ranged from similar to 20 to 85% of the total gamma delta T cells. Less than half of those were classified as WC1.1(+) or WC1.2(+) by mAb staining thus indicating a third major WC1(+) population. We found that naive gamma delta T cells proliferated in cultures of PBMC stimulated with antigens of Leptospira or Mycobacterium avium paratuberculosis (MAP) more than they did in control medium cultures or in those stimulated with M. bovis BCG antigens and that the responding gamma delta T cells included both WC1(+) and WC1(+) cells. In ex vivo PMA/ionomycin-stimulated cultures of WC1(+) gamma delta T cells but not WC1(+) cells produced both IL-17 and IFN gamma. In longterm cultures with Leptospira or MAP both WC1(+) and WC1(+) cells proliferated but only WC1 gamma delta T cells produced IL-17. In conclusion, goats have a substantial number of WC1and WC1(+) gamma delta T cells in PBMC that do not decrease with animal age after 6 months; both populations respond to bacterial antigens as naive cells but in these cultures only the WC1(+) gamma delta cells produc IL-17 and IFN gamma .

Automated summary

The study showed that goats have a significant number of WC1 and WC1(+) gamma delta T cells in PBMC that do not decrease with age after 6 months; both populations respond to bacterial antigens as naive cells, but in cultures, only WC1(+) gamma delta cells produce IL-17 and IFN gamma.