Human Interleukin 21 (IL21) Protein

Background

Interleukin 21 (IL21) is a potent cytokine produced primarily by activated CD4+ T cells, particularly T follicular helper (Tfh) cells and T helper 17 (Th17) cells. It belongs to the type I cytokine family and plays a critical role in regulating both innate and adaptive immune responses. IL-21 acts on a variety of immune cells, including B cells, T cells, natural killer (NK) cells, and dendritic cells (DCs), modulating their proliferation, differentiation, and functional activities. Its broad immunomodulatory effects make it a key regulator of immune homeostasis, inflammation, and host defense against pathogens and tumors. IL-21 is crucial for the development of germinal centers and the production of high-affinity antibodies, particularly through its regulation of B cell differentiation and antibody class switching. It also plays a significant role in promoting the cytotoxic activity of NK cells and CD8+ T cells, which are essential for anti-tumor and antiviral immunity