Interleukin-21 (IL-21) is a type I cytokine that has emerged as a potential immune therapeutic. IL-21 is a potent cytokine and survival factor for activated T cells and natural killer cells that acts on tumor-infiltrating lymphocytes and plays a role in immune response. In addition to its role in supporting the differentiation of CD4+ follicular helper T cells and T helper 17 cells, as well as antagonizing the differentiation of regulatory T cells, IL-21 can potentially enhance the function and long-term survival of antitumor cytotoxic CD8+ T cells.1-3

IL-21 is produced by activated CD4+ T cells and natural killer cells and signals via the IL-21 receptor (IL-21R). IL-21R is broadly expressed in hematopoietic cells including T and B lymphocytes, natural killer cells, and myeloid cells.1

Learn more about modalities targeting IL-21R:
bifunctional fusion proteins.

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CD: cluster of differentiation.


1. Shen S, Sckisel G, Sahoo A, et al. Front Immunol. 2020;11:832. doi:10.3389/fimmu.2020.00832. 2. Gattinoni L, Klebanoff CA, Restifo NP. Nat Rev Cancer. 2012;12(10):671-684. 3. Leonard WJ, Wan C-K. F1000Res. 2016;5:F1000. doi:10.12688/f1000research.7634.1.