Effects of in vivo thyroid hormone treatment on the expression of interleukin-2 receptors on avian splenocytes

Comell K strain chickens received a diet supplemented with 0, 0.1 and 1.0 ppm T-3 from the day of hatching. At 28 days of age, splenocyte suspensions were prepared and analyzed by flow cytometry for interleukin-2 receptor (IL-2R) and CD3 expression. The low T-3 dose increased the percentage of resting small cells expressing IL-2R while the mean fluorescence for this marker was enhanced only after mitogenic activation. This treatment did not alter the number of larger cells positive for IL-2R but did increase their mean fluorescence following mitogenic activation. The high T-3 dose depressed the numbers of cells positive for IL-2R and their mean fluorescence amongst all splenocyte preparations. Both levels of T-3 enhanced the numbers of CD3-positive cells in all cell preparations. These results suggest that the IL-2R expression can be modulated by in vivo T-3 supplementation and that these correlate with the previously demonstrated changes in IL-2-like activity. The regulation of IL-2R expression provides one mechanism through which thyroid status may regulate immune function.