Interleukin-25 （IL-25） – also known as interleukin-17E （IL-17E） – is a protein that in humans is encoded by the IL25 gene on chromosome 14. IL-25 is produced by many cell types. This cytokine can induce NF-κB activation, and stimulate the production of IL-8 （named also CXCL8）, which is the major chemotactic substance of neutrophils. Another important function of interleukin 25 is to support the Th2 immune response. IL-25 has been shown to induce the production of IL-4, IL-5 and IL-13. Because IL-25 promotes the development of a Th2 immune response, it acts to protect against several bowel infections caused by helminths. IL-25 is also referred to as the regulator of IL-9 production. Another function of IL-25 is the activation of natural lymphoid cells 2 （ILC2）.