Corticosteroid-interleukin 2 interactions: inhibition of binding of interleukin 2 to interleukin 2 receptors.

PHA activated human peripheral blood mononuclear cells (MNC) were incubated with human interleukin 2 (IL-2) in the absence or in the presence of 10(-6)-10(-9) M hydrocortisone (HC). HC suppressed the proliferative response of the activated MNC to highly purified human leucocyte IL-2 in a dose dependent manner. This suppression was in full accordance with an inhibition of the IL-2 binding capacity, whereby the high affinity binding sites were reduced by 85%, while the low affinity sites were less affected. The mechanism by which HC inhibits the binding of IL-2 is still unknown. Evidence is presented that HC binds only weakly to IL-2. We conclude that HC interferes with the IL-2 binding by modulating the binding and/or signal processing function of the IL-2 receptor.