TNF and inflammatory bowel disease: Similar to IL-6 in the present study, TNF-α serum levels are also not consistently found to be elevated in patients with IBD [36–40], despite the proven strong increase in mucosal TNF-α-producing cells and TNF-α levels in stool [16, 41–45] and the well-established efficacy of anti-TNF-α antibodies in CD and UC [46].