The 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 a cytokine called IL-2.

[3] The structure of the stable complex formed when IL-2 binds to the high affinity receptor has been determined using X-ray crystallography.

The structure supports a model wherein IL-2 initially binds to the α chain, then the β is recruited, and finally γ.

[3][4] Once IL-2 binds to the high affinity receptor, the complex is rapidly internalized and has only a short time to signal.

Thus, the concentration of IL-2 and its receptor available determines the tempo, magnitude and extent of T cell immune responses.