Interleukin-21: A pleiotropic mediator of immunity and inflammation with broad therapeutic potential

Abstract

Interleukin-21 (IL-21) is a member of the family of cytokines that share the common cytokine receptor γ-chain, γ c. IL-21 plays critical roles in the differentiation and function of multiple lymphoid and myeloid lineages. In this chapter, we review the inflammatory and immunosuppressive activities of this cytokine and the specific mechanisms by which this cytokine regulates both the innate and adaptive immune responses. Despite the fact that IL-21 and its receptor were only identified in 2000, a tremendous amount has been learned already, leading to the development of potential therapeutic approaches to cancer as well as potentially allowing for the specific manipulation of IL-21 effects in a spectrum of autoimmune diseases, allergic responses, and viral infections.