Rapid changes occur in the percentage of circulating bovine WC1(+) gamma delta Th1 cells

gamma delta T cells found in the peripheral blood of cattle include a major subpopulation distinguished by expression of WC1. These cells are distinct from the WC1(-) gamma delta T cell population based on T cell receptor gen e usage. We documented that a group of 6-month-old calves allowed free-rang e grazing and access to their mothers had a significantly greater proportio n of total gamma delta T cells in their blood, attributable to the WC1(+) g amma delta T cell subpopulation, compared to age and breed-matched calves h eld in conventional housing. When the animals with the greater proportion o f gamma delta T cells were transferred to conventional housing there was a decrease in the WC1(+) population so that by 3 weeks after transfer there w as no longer a significant difference between the two groups. To investigat e the biological activities of WC1(+) gamma delta T cells, the cells were p urified by flow cytometric sorting. In vitro, they responded to stimulation by irradiated monocytes in autologous mixed leukocyte reaction (AMLR) cult ures but not to direct stimulation through the T cell receptor (TCR) by ant i-delta monoclonal antibody. After stimulation in the AMLR, WC1(+) gamma de lta T cells had a Th1 cytokine profile characterised by production of IFN-g amma and lack of IL-4. Thus we propose that higher levels of the WC1(+) gam ma delta T cells may provide calves with a mechanism to produce Th1 cytokin es and that the level of these cells may be modulated according to environm ent or stress since both groups of calves were apparently disease-free. (C) 2000 Harcourt Publishers Ltd.