TNF and inflammatory bowel disease: NF-κB is a transcription factor downstream of the mitogen-activated protein kinase (MAPK) signaling pathway that induces the production of inflammatory cytokines such as TNFα, IL-1β, and IL-6, as well as the expression of pro-inflammatory enzymes such as cyclooxygenase-2 (COX-2) and inducible nitric-oxide synthase (iNOS), all of which are involved in the pathogenesis of IBD.