IL-2

Alias: Interleukin-2

IL-2 is a TH1 cytokine that plays a central role in the activation and proliferation of lymphocytes that have been primed by antigens. IL-2 is pivotal for the expansion of most T cells, NK cells, and B cells during various phases of their response. IL-2 is made during T cell activation and fuels the growth of activated T cells. Apart from its most important role to mediate antigen-specific T lymphocyte proliferation, IL-2 also modulates the expression of IFNγ and MHC antigens, stimulates proliferation and differentiation of activated B cells, augments NK cell activity, and inhibits granulocyte-macrophage colony formation. IL-2 signals though various signaling pathways that include the activation of JAK/STAT5, the RAS/MAPK, and the PI3 Kinase pathways. These activations make IL-2 a known potent T cell growth factor, inducer of lymphokine-activated killer activity, boosts the cytolytic activity of NK cells, augmentation of Ig production, and an essential factor for the development of TReg cells. Even though IL-2 is a TH1 cytokine, it is a critical regulator of TH2 in a STAT5-dependent manner and an inhibitor TH17 differentiation/development. IL-2 is an important serum biomarker in several pathological situations such as cancer, infectious diseases, transplant rejection, multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus and type I diabetes.