In vitro effects of dexamethasone on bovine CD25+CD4+ and CD25-CD4+ cells

This paper investigates the in vitro effect of dexamethasone on bovine CD25(high)CD4(+), CD25(low)CD4(+) and CD25(-)CD4(+) T cells. Only a small percentage of bovine CD25(high)CD4(+) (2-4%) and CD25(low)CD4(+) (1-2%) cells expressed Foxp3. Dexamethasone caused considerable loss of CD25(-)CD4(+) cells, but it increased the relative and absolute numbers of CD25(high)CD4(+) and CD25(low)CD4(+) lymphocytes, while at the same time reducing the percentage of Foxp3(+) cells within the latter subpopulations. Considering all these, as well as the intrinsically poor Foxp3 expression in bovine CD25(+)CD4(+), it can be concluded that the drug most probably increased the number of activated non-regulatory CD4(+) lymphocytes. It has been found that changes in cell number were at least partly caused by proapoptotic effect of the drug on CD25(-)CD4(+) cells and antiapoptotic effect on CD25(high)CD4(+) and CD25(low)CD4(+) cells. The results obtained from this study indicate that the involvement of CD4(+) lymphocytes in producing the anti-inflammatory and immunosuppressive effect of dexamethasone in cattle results from the fact that the drug had a depressive effect on the production of IFN-gamma by CD25(-)CD4(+) cells. Secretion of TGF-beta and IL-10 by CD4(+) lymphocytes was not involved in producing these pharmacological effects, because the drug did not affect production of TGF-beta and, paradoxically, it reduced the percentage of IL-10(+)CD4(+) cells. (C) 2012 Elsevier Ltd. All rights reserved.