Differential regulation of lymphokine production by distinct subunits of the T cell interleukin 2 receptor

Most biologic responses to IL-2 have been attributed to interaction of IL-2 with a high affinity receptor which consists of a heterodimer composed of two distinct IL-2-binding proteins (IL-2Rα/IL-2Rβ). However, both low affinity IL-2Rα (55 kD) and intermediate affinity IL-2Rβ (70-75 kD) also appear to be expressed independently on the cell surface. We investigated the receptor-specific regulatory effects of IL-2 on cytokine production in unstimulated and activated T cells. T cells were activated by stimulation of the antigen receptor complex with anti-CD3 mAb. IL-2 (10² U/ml, 1 nM) stimulation of resting cells resulted in a fivefold increase in GM-CSF release but in only minimal IFN-gamma release. IL-2 markedly augmented mRNA expression of GM-CSF but not IFN-gamma in unstimulated T cells. IL-2Rβ mAb but not IL-2Rα mAb decreased IL-2-induced GM-CSF release and mRNA expression from unstimulated T cells. IL-2 concentrations required for GM-CSF release from resting cells suggested ligand binding to an intermediate affinity receptor. GM-CSF and IFN-gamma release from activated T cells increased four- to fivefold in response to 1 nM IL-2 and IL-2 augmented both GM-CSF and IFN-gamma mRNA. IL-2Rβ mAb but not IL-2Rα mAb reduced GM-CSF release and mRNA expression in activated T cells stimulated with 1 nM IL-2. IL-2Rα blockade markedly decreased IL-2-induced IFN-gamma release and mRNA expression from activated cells, while IL-2Rβ blockade had little effect on IFN-gamma production in activated cells. IL-2Rα blockade altered the affinity of the receptor mediating activated cell GM-CSF release from a high affinity to an intermediate affinity state. These studies indicate an independent role for IL-2Rβ in mediating GM-CSF production from T cells. They also suggest that unstimulated and activated T cells, which express distinct IL-2 receptor moieties, mediate release of separate lymphokines and that different subunits of the IL-2 receptor may play an important role in the regulation of cytokine production.