Interleukin 17B (IL-17B) predicts a molecular mass of 20.4 kDa, is expressed in several peripheral tissues and immune tissues. In contrast to the high level of IL-6 secretion stimulated by IL-17A, IL-17B failed to induce IL-6 secretion in fibroblasts; however, it significantly enhanced the TNF-α-induced production of G-CSF and IL-6 in the fibroblasts.