Recurrent Crohns disease originates with small erosions in the follicle-associated epithelium overlying the Peyers patches. Animal studies have illustrated mucosal immune regulation by dendritic cells located in the subepithelial dome. The aim of this study was to characterize the dendritic cells at this specific site in patients with Crohns disease. Heal tissues were obtained after surgery performed on Crohns patients; ileal samples from noninflammatory bowel disease and ulcerative colitis served as standard and inflammatory controls, respectively. Flow cytometry of isolated intestinal mononuclear cells showed a larger subset of dendritic cells in Crohns samples compared with controls. This finding was corroborated by confocal microscopy, showing enhanced infiltrates of cells positive for the dendritic cell markers, DC-SIGN (+) and CD83 (+), in the subepithelial dome. Moreover, the CD83 (+) cells in Crohns tissues showed reduced expression of the lymph node migratory receptor, CCR7, possibly contributing to the high numbers of dendritic cells. After exposure to nonpathogenic Escherichia coli in Ussing chambers, dendritic cells in the subepithelial dome of Crohns disease demonstrated increased co-localization with translocated bacteria. Immunohistochemical results revealed that DC-SIGN (+) cells in Crohns tissues were found to express toll-like receptor 4 and produce tumor necrosis factor-a. In conclusion, nonmigrating dendritic cells that accumulate in the subepithelial dome and internalize nonpathogenic bacteria may be important for the onset and perpetuation of mucosal inflammation in Crohns disease.