At the protein level, the adhesion molecules ICAM1 and ITGB2 are up-regulated in both compartments, while ITGB3 is only up-regulated in the mucosa, and PECAM1 is only up-regulated in the submucosa/wall, consistent with their role in mediating leukocyte trafficking in the inflamed gut [33] as well as predicting flares in IBD [34,35]. Here, PECAM1 is linked to inflammatory bowel disease.