IL-17B is a member of IL17 famaily, was originally described as a proinflammatory cytokine. IL-17B is produced by neutrophils and potentiates TNF-α effect on the production of cytokines and chemokines, such as IL-6, G-CSF, and CCL20, known to control immune cell trafficking to inflamed tissues. Interestingly, although IL-17B and IL-17E (IL-25) share a common receptor, IL-17RB, IL-17B, and IL-17E deficiency lead to opposite results in a model of acute colitis induced by dextran sulfate sodium. IL-17B inhibits IL-17E binding to IL-17RA– IL-17RB complexes on epithelial cells, and limits IL-17E-induced IL-6 production by colon epithelial cells.