IL-2R is a heterotrimeric protein binds and responds to the cytokine IL-2. Three distinct chains of IL-2R, termed as α, β and γ, which are non-covalently associated are identified. The α and β chains are involved in binding IL-2, while signal transduction following cytokine interaction is carried out by the γ chain, along with the β subunit. The α chain of the IL-2R can bind to the β chain before receptor interaction with IL-2. The γ chain alone has a very weak affinity for IL-2, but after the ligand is bound to the α/β heterodimer, the γ chain becomes recruited to the complex to form a very stable macromolecular quaternary ligand/receptor complex. Interleukin-2 receptor subunit gamma (IL2RG), also known as cytokine receptor common subunit gamma, CD antigen CD132, gammaC, p64, which belongs to the type I cytokine receptor family or type 5 subfamily. IL2RG is located on the surface of immature blood-forming cells in bone marrow. Defects in IL2RG are the cause of severe combined immunodeficiency X-linked T-cell-negative/B-cell-positive/NK-cell-negative (XSCID).