TNF and colitis: In addition to epithelial cell damage, macrophages play an important role in the pathogenesis of colitis, and stimulated and subsequently activated proinflammatory M1 macrophages not only cause direct colonic mucosal injury via the secretion of proinflammatory cytokines such as TNF-α, IL-1β, and IL-6, but also cause the infiltration of neutrophils and CD4+ Th cells into the mucosal epithelium via the secretion of IL-23 (41).