Dexamethasone, but not meloxicam, suppresses proliferation of bovine CD25plus CD4plus and CD25-CD4plus 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 CD25lowCD4⁺ T cells cannot be the result of enhanced proliferation of these cells.