The γ c Family of Cytokines: A Pleiotropic Family That Controls Proliferation, Survival, and Differentiation

Interleukin-2 (IL-2), IL-4, IL-7, IL-9, IL-15, and IL-21 represent a family of cytokines that share the common cytokine receptor γ chain, γ c , as a key receptor component. These are all type I cytokines, which have a similar four α-helix bundle structure. Together these cytokines exhibit a broad range of actions that include regulating cell proliferation, survival, cytolytic activity, and differentiation. Their target cells span a large range of immune cells, including, for example, T cells, B cells, natural killer cells, and dendritic cells. Because of the breadth of their immunoregulatory actions, these cytokines collectively have actions related to the control of cancer, autoimmune disease, and immunodeficiency, and as such are of substantial clinical interest.