In chronic diseases such as Ulcerative Colitis (UC), a major form of inflammatory bowel disease (IBD), alterations of MUC2 function and glycosylation are well known (26, 27, 28) and animal models have shown definitively that Muc2 and its O-glycans in mice are essential for mucosal barrier function, and protection from microbiota-dependent colitis, colon cancer, and infection (9, 12, 24, 29, 30). Here, MUC2 is linked to irritable bowel syndrome.