The proinflammatory interleukin-21 elicits anti-tumor response and mediates autoimmunity

Interleukins (IL) are inflammatory proteins (except IL-4 and IL-10) that modulate the immune system (1-4). IL-21 induced inflammation in vivo, based on recruitment of neutrophil and monocyte populations (5-8). This cytokine is similar in primary sequence and structure to IL-2 and IL-15 and is a member of the type I cytokine superfamily which includes IL-2, IL-4, IL-7, IL-9, IL-11, IL-12, IL-13, IL-15 and Colony Stimulating Factors (CSFs). IL-21 is a multifunctional cytokine having roles in both in-nate and adaptive immune responses of the Th1 type (9-11) with an effect on proliferation, apoptosis and differentiation of T cells, NK cells, dendritic cells and B cells (12-15) and lymphocytes function (16-18) (Fig. 1). IL-21, like other members of this fam-ily, is a gamma-chain dependent cytokine playing a prominent role in promoting and maintaining T cell populations (19-21). Human and murine ...