The current work also calls attention to the unique features of NEC, including differences in the location of disease along the gastrointestinal tract (NEC is an ileal disease while colitis affects the colon), age (NEC occurs in the newborn period whereas these other models occur in older mice), as well as differences in microbial ligands which may be present in models of colitis versus NEC, and which could activate AHR. This evidence concerns the gene AHR and colitis.