IL21 is a pleiotropic cytokine produced by CD4+ T cells in response to antigenic stimulation. Its action generally enhances antigen-specific responses of immune cells. The biological effects of IL21 include induction of differentiation of T-cells-stimulated-B-cells into plasma cells and memory B-cells, stimulation (in conjunction) with IL4 of IgG production, and induction of apoptotic effects in naive B-cells and stimulated B-cells in the absence of T-cell signaling. Additionally, IL21 promotes the anti-tumor activity of CD8+ T-cells and NK cells. IL21 exerts its effect through binding to a specific type I cytokine receptor, IL21R, which also contains the gamma chain (?c) found in other cytokine receptors including IL2, IL4, IL7, IL9 and IL15. Alternative Names: IL-21 protein, IL21, IL-21, IL-21 protein, IL 21 protein, Interleukin 21 protein, IL 21