Increased levels of inflammatory cytokines, including interleukin (IL)-6, IL-1β, IL-8, and tumor necrosis factor (TNF)-α, have been reported in the blood and serum of IBS model animals and IBS patients (Dinan et al. 2006; Liebregts et al. 2007; Heel et al. 2002). Here, TNF is linked to irritable bowel syndrome.