Interleukin-2 receptor (IL-2R) is a heterotrimeric protein expressed on the surface of certain immune cells, such as lymphocytes, that binds and responds to the cytokine IL-2. The IL-2R is made up of 3 subunits - alpha (α), beta (β) and gamma (γ). 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 β and γ chains of the IL-2R are members of the type I cytokine receptor family. IL-2R has a high binding affinity to IL-2 and is expressed by antigen-activated T lymphocytes (T cells). IL-2 Rα is also known as CD25, p55, and Tac (activated T cell) antigen.

> 95% as determined by SDS-PAGE; > 95% as determined by HPLC