Figure 1.

IL-4 receptor alpha (IL-4Rα) constitutes subunits of two heterodimeric receptors, named type I and type II receptors. The type I receptor, composed of IL-4Rα and common cytokine receptor γ-chain (γc), interacts only with IL-4. The type II receptor is formed from IL-4Rα and IL-13Rα1 subunits and interacts with either IL-13 or IL-4. IL-13 also displays the capacity to bind IL-13Rα2, which is regarded as a decoy receptor. A binding of a ligand by type I and II receptors results in an activation of Janus family kinases (JAK1, JAK2, and JAK3) followed by phosphorylation of a signal transducer and activator transcription 6 (STAT6).