Interleukin 2: from immunostimulation to immunoregulation and back again

Interleukin 2 (IL‐2) was one of the first cytokines to be discovered. However, the complex role of IL‐2 and its receptor in the regulation of immune responses is only now emerging. This review explores the various signals triggered by IL‐2 and discusses their translation into biological function. A model is outlined that accommodates the seemingly contradictory functions of IL‐2, and explains how one cytokine can be an essential T‐cell growth and differentiation factor and yet also be indispensable to maintain peripheral tolerance.

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