IL-2 is produced primarily by antigen activated T-cells. It is critical to clonal expansion of various lymphocytes. It is also a strong mediator of the immune response of other cell types. IL-2 is known to stimulated proliferation in T-cells, thymocytes, B-cells, monocytes, oligodendrocytes, NK cells and will stimulate cytokine production by many of these cells.

IL-2 receptor is a complex composed of 3 subunits. The alpha subunit is specific for IL-2, while the beta and gamma subunits generally remain pre-complexed and are shared by the IL-15 receptor. The gamma subunit is also shared by IL-4, IL-7 and IL-9 receptors. The receptor can also be found in a soluble form in serum often very rapidly neutralizing IL-2 in serum.

In summary, IL-2 is One of the most studied and more important cytokines in immunity. It is critical to the activation and clonal expansion of the immune system in response to foreign antigen. It is often assayed in parallel with other TH1/TH2 differentiation, expansion ,and decision factors, such as IL-4, IL-6, IL-10, IL-12, IL-15, TNFa, and IFNy.