Shown are the receptors for IL-2, IL-4, IL-7, IL-9, IL-15, IL-21, and TSLP. IL-2 and IL-15 are the only two of these cytokines to have three receptor chains. These two cytokines share IL-2Rβ, whereas IL-7 and TSLP share TSLPR, and of the cytokines shown, only TSLP does not share γc. There are three classes of IL-2 receptors, binding IL-2 with low affinity (IL-2Rα alone), intermediate affinity (IL-2Rβ + γc), and high affinity (IL-2Rα + IL-2Rβ + γc); only the high affinity IL-2 receptor is shown in the figure. Each γc family cytokine activates JAK1 and JAK3, whereas TSLP was reported to not activate any JAK kinase,. The major STAT proteins activated by these cytokines are shown. STAT5 refers to both STAT5A and STAT5B.