Effect of cyclosporin A and dexamethasone on interleukin 2 receptor gene expression.

Here we demonstrate that CsA and DEX, at concentrations that markedly inhibited PHA-induced proliferation and IL 2 mRNA accumulation, partially diminished the expression of receptors for IL 2 on PBMC. This inhibition of IL 2 receptor expression occurred at a pretranslational level and involved a reduction in both high affinity and low affinity forms of the receptor. Although both CsA and DEX inhibited IL 2 receptor expression by about 50%, only CsA blocked the PHA-mediated induction of IL 2 responsivity in PBMC cultures. These data provide evidence that 1) CsA and DEX suppress the proliferation of T lymphocytes through distinct (though perhaps overlapping) mechanisms, 2) CsA (but not DEX) blocks the PHA-mediated induction of signals necessary for T cells to become capable of proliferating in response to IL 2, and 3) T cells regulate the expression of their genes for IL 2 and IL 2 receptors, at least in part, through independent mechanisms.