Interleukin-25 (IL-25) is a protein that in humans is encoded by the IL25 gene.

The protein encoded by this gene is a cytokine that shares sequence similarity with interleukin 17. This cytokine can induce NF-kappaB activation, and stimulate the production of interleukin 8. Both this cytokine and interleukin 17B are ligands for the cytokine receptor IL17BR. Studies of a similar gene in mice suggest that this cytokine may be a pro-inflammatory cytokine favoring the Th2-type immune response. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Mar 2010].
Function: Induces activation of NF-kappa-B and stimulates production of the proinflammatory chemokine IL-8. Proinflammatory cytokine favoring Th2-type immune responses.