Ulcerative colitis (UC), a common form of inflammatory bowel disease (IBD), is a chronic, idiopathic intestinal disorder affecting close to a million patients in the United States. The pathogenesis of UC involves immune dysregulation in response to commensal microbes in genetically susceptible individuals. Recently, the severity of inflammation has been correlated with increased IL-9 production and elevated populations of mucosal TH9 T-cells. Unfortunately, our understanding of IL-9’s contribution to the pathogenesis of UC has been hampered by contradictory findings between animal and human studies. To overcome these challenges, we are developing more accurate in vitro models of the intestine using Organs-on-Chips technology that place living human cells in micro-engineered environments. Our Intestine-Chip recapitulates key aspects of the intestinal milieu including mechanical forces, extracellular matrix, tissue-tissue interfaces, immune cells, and blood components.