Mouse Anti-Human IL-21 Antibody (S-3523)

Interleukin-21 (IL-21) is a four-α-helical-bundle type I cytokine produced mainly by activated CD4⁺ T helper cells, NKT cells and TFH cells that signals through a heterodimeric receptor composed of the IL-21R and the common γ-chain (γc) to activate JAK1/JAK3–STAT1/STAT3 pathways, thereby orchestrating a broad immunomodulatory program that drives the differentiation, proliferation and effector function of B cells into long-lived plasma cells and memory B cells, promotes the development of Th17 and Tfh subsets while suppressing Treg stability, enhances cytotoxic activity and survival of CD8⁺ T cells and NK cells, and synergizes with IFN-γ or IL-15 to amplify antiviral and antitumor immunity, making it a key molecular hub whose dysregulation contributes to autoimmune pathologies such as systemic lupus erythematosus and type 1 diabetes and whose exogenous delivery or blockade is being therapeutically exploited in cancer immunotherapy, chronic viral infections and allergy.