Progress on Interleukin-21

Interleukin-21 is a novel cytokine that regulates the proliferation of T and B cells,and involves the maturation and expansion of NK cells.IL-21 is produced by activated T cell,and is a four-helix-bundle type I cytokine.IL-21 has various biological activities that affect T and NK cell function,antitumor activity,immunoglobulin production,Th1 response,and Th2 response.IL-21 is thought to be a mediator cytokine,which promotes the transition from innate immunity to adaptive immunity.Currently,human,mouse,bovine and porcine IL-21 have been cloned and invested.It is a potential way to cure tumor and enhance innate immunity response and adaptive immunity response.The biological function,signal transmission mechanism and molecular structure of IL-21 were reviewed.