Association of the common gamma-chain with the human IL-7 receptor is modulated by T cell activation.

IL-7 acts on both resting and activated T cells. The functional IL-7R is reported to consist of two subunits, the ligand binding IL-7R and the common gamma-chain (gamma c chain), where IL-7R:gamma c chain association is driven solely by ligand binding. However, we now demonstrate that in primary T cells this event is also controlled by cellular activation. We show that IL-7R:gamma c chain complexes are detected in activated, but not in resting, T cells despite similar levels of gamma c chain expression, implying that the gamma c chain is not associated with the IL-7R in unstimulated T cells. Furthermore, IL-7R:gamma c chain association correlates with the expression of JAK-3 in T cells, but not in transfected COS-7 cells. The finding that IL-7R:gamma c chain assembly is controlled at a level beyond that of receptor expression has important implications for the control of cytokine function in T cells.