Description
Interleukin 21 (IL-21) is normally expressed by activated CD4+ T cells. The IL-21 receptor activates the JAK/STAT signaling pathway and is expressed on T, B, and natural killer (NK) cells. IL-21 cooperates with IL-4 for the production of multiple antibody classes in B cells. IL-21 has pleiotropic effects on the proliferation, differentiation, and effector functions of B, T, NK, and dendritic cells