Cell-mediated immune function in lambs chronically treated with dexamethasone.

Crossbred ewe and wether lambs were individually stanchioned in environmentally controlled rooms at 20 degrees C. On d 0, lambs were treated with .04 mg of dexamethasone (DEX; n = 10)/kg of BW or given an equal volume of saline vehicle (SAL; n = 10). Treatment was repeated every 48 h for 14 d. Samples of blood were obtained by puncture of the jugular vein on d 0 (before treatment), 2, 4, 7, 10, and 14. Total and differential leukocyte numbers, lymphocyte blastogenic responses to mitogens, and in vitro production of interleukin-2 (IL-2) were determined. No treatment x day interaction was noted for any of the experimental end points (P greater than .10); therefore, within-day comparisons between DEX- and SAL-treated lambs were not made. However, over all 14 d, DEX-treated lambs had increased (P less than .05) numbers of lymphocytes (6.5 +/- .4 vs 5.1 +/- .4 x 10(3) cells/microliters for SAL) and monocytes (.8 +/- .1 vs .6 +/- .1 x 10(3) cells/microliters for SAL), and these increases contributed to an increase (P less than .01) in total leukocytes (11.2 +/- .5 vs 9.1 +/- .5 x 10(3) cells/microliters for SAL). Lymphocyte blastogenic responses to mitogens were not affected by DEX treatment. Production of IL-2 was reduced (P less than .05) for DEX- (.90 +/- .12 units/ml) compared with SAL-treated lambs (1.27 +/- .13 units/ml). The data suggest that continued treatment of lambs with DEX may result in a modest reduction in production of IL-2, but mitogen-stimulated blastogenic responses of lymphocytes are not reduced by DEX treatment.