**3.3 Inflammatory bowel disease**

Inflammatory bowel diseases (IBD) include Ulcerative colitis (UC) and Crohn's disease (CD). Although the main manifestations of ulcerative colitis are mainly limited to the colon, Crohn's disease is a systemic disease that can affect any organ in the body. The exact cause of either UC or CD remains unknown and is presumed to be environmental [46, 56, 57]. However, what is common in the pathogenesis of UC and CD is the failure of the innate immune system. In UC, there is dysbiosis with an overgrowth of pathogenic organisms. The pathogens are recognized as foreign by the Paneth cells, leading to an inflammatory response in the bowel wall [9]. Some cases of Crohn's disease are due to genetic defects, which diminishes the ability of Paneth cells to sense and regulate the gut microbiome. Mutation of NOD 2 receptor is linked with the development of CD as the Paneth cells of the affected individuals in CD cannot secrete sufficient antimicrobial peptides to prevent dysbiosis [57].
