Effect of dexamethasone and meloxicam on counts of selected T lymphocyte subpopulations and NK cells in cattle - In vivo investigations

The purpose of these investigations has been to assess the in vivo effect of dexamethasone (DEX) and meloxicam (MEL) on percentages and absolute counts of cells within selected T lymphocyte subsets and NK cells in cattle. DEX application caused substantial loss of NK, CD4+, CD8+ and WC1+ T cells, but the drug's influence on T-cell count was selective, that is it varied according to the presence and intensity of CD25 expression. Reduced counts of T lymphocytes were due to the depletion of CD25−CD4+, CD25−CD8+ and CD25−WC1+ T cells. The loss of CD25−CD8+ and CD25−WC1+ T cells was a deep and lasting disorder, whereas the depletion of CD25−CD4+ T cells was manifested less strongly and regressed promptly. The administration of DEX did not affect absolute counts of CD25lowCD4+ and CD25lowCD8+ T cells, but induced an increase in percentages and absolute counts of CD25highCD4+, CD25highCD8+, CD25lowWC1+ and CD25highWC1+ T cells. In respect of the effect on counts of CD4+, CD8+ and WC1+ T cells, MEL proved to be a safe medication, because it did not alter counts of these lymphocytes. The administration of MEL led to an increase in the absolute count of NK cells, but the effect did not appear quickly and its development required time.