In Crohn's disease, the lining of the small intestine is abnormally colonized by E. coli organisms that are able to adhere to and invade intestinal epithelial cells. In a study appearing online on May 24 in advance of publication in the June print issue of the Journal of Clinical Investigation, Arlette Darfeuille-Michaud and colleagues from Universit d'Auvergne, France, show that the adherent-invasive E. coli (AIEC) adhere to a region of intestinal epithelial cells known as the brush border in patients with Crohn's disease, but not in healthy individuals. They show that this adhesion is dependent on the expression of the receptor CEACAM6 (carcinoembryonic antigenrelated cell adhesion molecule 6) on the surface of the epithelial cells. They go on to show that CEACAM6 expression is increased in Crohn's disease patients after infection with AIEC bacteria, indicating that this organism can promote its own colonization in individuals with Crohn's disease. The authors conclude that CEACAM6 expression in individuals with inflammatory bowel disease could be used as a diagnostic marker for Crohn's disease.