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. 2021 Jan 13;22(2):727. doi: 10.3390/ijms22020727

Figure 1.

Figure 1

Receptor types and signal transduction of IL-4R and IL-13R. There are three different kinds of IL-4 receptors. IL-4 binds to the IL-4Rα chain, then recruits the IL-2Rγ-common (γc) chain (type I IL-4R) or the IL-13Rα1 chain (type II IL-4R) to form a receptor complex that can initiate signal transduction. The type III IL-4R consists of all three chains. IL-13 also have three different receptors. IL-13 receptor type I (IL-4Rα/IL-13Rα1/IL-13Rα2) and type II (IL-4Rα/IL-13Rα1) are expressed in solid tumors, while type III (IL-4Rα/IL-13Rα1/γc) is expressed in hemocytes only. IL-13 binds IL-13Rα1 with a low affinity and complexes with the IL-4Rα (type II receptor). IL-13 binds to the IL-13Rα2 with a high affinity. IL-13 can bind to a soluble IL-13Rα2 receptor, which has no downstream signaling, or bind to transmembrane IL-13Rα2 and activate AP-1. Figure sketch adapted from reference [27].