For IBD patients that display increased intestinal paracellular permeability, TNF-α levels become elevated in the intestinal mucosa, serum, and stools of these patients (47), with recent in vitro studies further suggesting that increased TNF-α impairs the intestinal tight junction barrier via upregulation of the myosin light-chain kinase protein expression (37, 52). Here, TNF is linked to irritable bowel syndrome.