Selenium status and phytohemagglutinin-stimulated T lymphocytes from beef calves

The effect of selenium (Se), supplemented by subcutaneous injections, upon in vitro phytohemagglutinin (PHA)-stimulated T lymphocyte blastogenesis was evaluated in crossbred calves at 45, 124, and 270 d of age. Peripheral blood lymphocytes (5×10(5)) obtained from control (n=4) and Se-treated (n=4) calves were cultured with 0, 0.4, and 0.8 μg PHA and 0.5 μCi [(3)H]-thymidine in a complete culture medium. At 60h, cultures were harvested for the quantitation of thymidine incorporation. The degree of lymphocyte blastogenesis or stimulation to PHA, expressed as the stimulation index (SI), was assessed for treatment and age effects. At the onset and end of the experimental period, plasma Se and blood glutathione peroxidase concentrations revealed that control calves [0.045 ppm and 48.4 units/g hemoglobin (Hb), respectively] were marginally deficient and treated calves (0.075 ppm and 143.0 units/g Hb, respectively) were adequate in Se status. The SI values were not influenced (P>0.01) by Se treatment, but were affected (P<0.003) by age. For combined treatments and PHA dosages, mean SI values were greater (P<0.05), when lymphocytes were tested at 45 (SI=25.9) than at 124 and 270 (SI=13.7 and 15.5, respectively) d of age. Lymphocyte viability and number were not affected by Se treatment, but lymphocyte number tended (P<0.1) to increase with age. In conclusion, T lymphocyte responsiveness to mitogen stimulation was normal in beef calves residing in a geographical area considered deficient in Se.