Any abnormal activation of such immune cells (macrophages) overproduces the inflammatory cytokines e.g., tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 that cause destructive cell damage to the intestinal epithelial monolayers and subsequent mucosal inflammation leading to inflammatory bowel disease (IBD) such as Crohn's disease (CD) and ulcerative colitis (UC) [18,19]. This evidence concerns the gene TNF and Crohn disease.