Recombinant human IL-9 protein - Bioactive cytokine

Originally identified as a growth factor of T cells and mast cells, Interleukin-9 (IL-9) is now regarded as a multifunctional cytokine that regulates the function of many different cell types and plays an important role in immunity and immune pathogenesis [1-3]. IL-9 is a secreted cytokine produced by a wide variety of cells, including mast cells, natural killer T (NKT) cells, Th2, Th17, Treg, and Th9 cells. It supports the growth of activated T cell subsets and promotes mast cell proliferation and differentiation [1, 2]. In addition, IL-9 has a direct effect on epithelial cell function, stimulating the production of mucin and T cell chemoattractants [2-4]. 

IL-9 signals through the heterodimeric cell surface IL-9 receptor (IL-9R) consisting of IL-9Rα (also called CD129) and IL-2Rγ (also called the common γ-chain or CD132). The binding of IL-9 to its receptor triggers three main signaling pathways: JAK/STAT, MAPK, and PI3K [1, 2]. IL-9 is an interesting therapeutic target as it plays a critical role in immunity to parasitic infections, the pathogenesis of cancer and immuno-pathological conditions such as asthma [5, 6].  

To date, its main role has been found in the immune responses in allergic diseases, such as asthma and bronchial hyperreactivity. IL-9 promotes the survival, proliferation, and activation of mast cells and other immune cells, which are central to the development of allergic reactions and inflammatory diseases [7].

1. Ritobrata G. & Kaplan M.H., 2011. A brief history of IL-9. J Immunol. 186(6):3283-8.
2. Chakraborty S. et al., 2019. An update on interleukin-9: From its cellular source and signal transduction to its role in immunopathogenesis. Int J Mol Sci. 20(9):2113.
3. Longphre M. et al., 1999. Allergen-induced IL-9 directly stimulates mucin transcription in respiratory epithelial cells. J Clin Invest . 104(10):1375-82.
4. Little F.F. et al., 2001. Il-9 stimulates release of chemotactic factors from human bronchial epithelial cells.Am J Respir Cell Mol Biol . 25(3):347-52.
5. Silva N.S.L. et al., 2021. Interleukin-9 in immunopathology of Trypanosoma cruzi experimental infection. Front Cell Infect Microbiol. 11:756521. 
6. Patrussi L. et al., 2021. Interleukin (IL)-9 supports the tumor-promoting environment of chronic lymphocytic leukemia. Cancers (Basel). 13(24):6301.
7. Bick F, et al., 2025. A reappraisal of IL-9 in inflammation and cancer. Mucosal Immunol. (1):1-15.