Interleukin 2

Interleukin 2 (IL-2) is an interleukin, a type of cytokine signaling molecule in the immune system. It is a protein that regulates the activities of white blood cells (leukocytes, often lymphocytes) that are responsible for immunity. IL-2 is part of the body's natural response to microbial infection, and in discriminating between foreign ("non-self") and "self". IL-2 mediates its effects by binding to IL-2 receptors, which are expressed by lymphocytes.

Signaling pathway

IL-2 is a member of a cytokine family, each member of which has a four alpha helix bundle; the family also includes IL-4, IL-7, IL-9, IL-15 and IL-21. IL-2 signals through the IL-2 receptor, a complex consisting of three chains, termed alpha, beta and gamma. The gamma chain is shared by all members of this family of cytokine receptors.

The IL-2 Receptor (IL-2R) α subunit has low affinity for its ligand but has the ability (when bound to the β and ϒ subunit) to increase the IL-2R affinity 100-fold. Heterodimerization of the β and ϒ subunits of IL-2R is essential for the signalling in T cells.