[Effect of dexamethasone on the human interleukin-2 receptor alpha chain gene expression]

Glucocorticoids have wide effects on the immune system, the mechanisms of these effects have not been clearly defined. The interaction of interleukin-2 (IL-2) with its receptor (IL-2R) is a critical control point in the T-cell mediated immune response. The effect of dexamethasone, a synthetic glucocorticoid hormone, on IL-2R is unclear in comparison with its inhibition on the accumulation of IL-2 mRNA. Our study shows that dexamethasone increases the basal and PHA-induced mRNA levels of IL-2R alpha gene in Jurkat cells, but it does not affect the expression of reporter gene constructs containing 5' flanking sequences (-482bp/ +16bp or -350bp/+16bp) of the IL-2R alpha gene in PHA activated Jurkat cells. These results indicate that dexamethasone plays a positive regulatory role in the IL-2R alpha gene expression, but the effect is not mediated by the previously identified proximal regulatory elements located between -482bp/+1bp. Meanwhile, our results also provide evidence that the activation mechanism of dexamethasone is different from that of PHA, and that dexamethasone and PHA show a synergistic effect in the induction of IL-2R alpha gene expression.