Interleukin-25 (IL-25), also known as IL-17E, is a 17kD protein and a recently identified member of the IL-17 cytokine family. This cytokine is secreted by a variety of cells, including type 2 helper T cells (Th2), bone marrow-derived mast cells and alveolar macrophages2. On target cells, IL-25 can induce the production of several type 2 cytokines including IL-4, IL-5 and IL-13 and implicates a role for this cytokine in type 2 immune response3. Studies have linked this cytokine to promoting airway hyperreactivity, limiting pro-inflammatory cytokine production and chronic intestinal inflammation and providing protective immunity following intestinal helminth infection4-6.