Dexamethasone, but not meloxicam, suppresses proliferation of bovine CD25+ CD4+ and CD25- CD4+ T cells.

Recently, we found that dexamethasone caused a depletion of CD25- CD4+ T cells, but it increased the number of CD25highCD4+ and CD25lowCD4+ T cells. We also determined meloxicam-induced increase in the number of CD25highCD4+ T cells. In view of this, and taking into consideration the latest reports indicating that meloxicam shows an anti-proliferative effect on bovine peripheral blood mononuclear cells, it was considered purposeful to determine the effect of both drugs on proliferation of bovine CD25highCD4+, CD25lowCD4+ and CD25- CD4+ T cells. Flow cytometry analysis and 5-bromo-2'-deoxyuridine incorporation assay were applied to detect the cell proliferation. It was demonstrated that dexamethasone, but not meloxicam, significantly reduced cell proliferation within all three evaluated CD4+ T cell subpopulations. Thus, the depletion of CD25- CD4+ T cells by treatment with dexamethasone can partly be the effect of the anti-proliferative action of the drug, however, dexamethasone-induced increase in the number of CD25highCD4+ and CD25IowCD4+ T cells cannot be the result of enhanced proliferation of these cells.