Human Interleukin 9 (IL9) Protein

Background

Interleukin-9 (IL9) is a multifunctional cytokine belonging to the type I cytokine family. Originally classified as a T cell growth factor, IL-9 has since been found to influence a variety of immune cells, including T cells, B cells, mast cells, eosinophils, and epithelial cells. Produced predominantly by a subset of CD4+ T cells known as Th9 cells (T helper 9), IL-9 is involved in many immune responses, particularly those related to allergies, asthma, and parasitic infections. The discovery of IL-9’s wide range of biological activities, from promoting inflammation to supporting tissue repair, has highlighted its dual role as both a protective and pathogenic cytokine. This ambivalence makes IL-9 a key player in immune regulation. While it is essential in protective immunity, especially against helminth infections, its dysregulation is implicated in various allergic diseases and autoimmune disorders, making it a target of therapeutic interest.