Interleukin-2 (IL2) is an interleukin, or hormone of the immune system that is instrumental in the body's natural response to microbial infection and in discriminating between foreign (nonself) and self. IL2 mediates its effects by binding to IL2 receptors, which are expressed by lymphocytes, the cells that are responsible for immunity.

Discovery and Characterization

The IL2 molecule was first characterized as a variably glycosylated 15,500 Dalton protein capable of supporting long-term T lymphocyte (T cell) proliferation (Robb, R. & Smith,K.A. 1981), and was first purified to homogeneity by immunoaffinity chromatography (Smith, K.A., et. al., 1983). The IL2 molecule was also the first interleukin found to be encoded by a complimentary DNA (cDNA)(Taniguchi, T. et. al. 1983), and to mediate its effects via specific IL2 receptors (Robb, R. et. al., 1981). Thus, despite being designated the number 2 interleukin, it was the first interleukin molecule, gene and receptor to be discovered. It was designated number 2 because data at the time indicated that IL1, produced by macrophages, facilitates IL2 production by T lymphocytes (T cells) (Smith, K.A., et.al. 1980).