IL-4R alpha is a Type I transmembrane protein belonging to the class I cytokine receptor family and is a component of two different receptor complexes. When associated with the common gamma chain, which is required for signaling, it binds IL-4 with higher affinity. When complexed with IL-13R alpha I, interaction with both IL-4 and IL-13 is enabled. Through JAK/STAT signal transduction pathways, cell-specific responses including Th2 differentiation, mucosal immunity, allergic inflammation and IgE production result. The soluble form of IL-4R alpha, generated through proteolysis in the human, retains biologic activity and is able to antagonise IL-4.