The gastrointestinal tract absorbs nutrients through the intestinal epithelium while controlling the resident bacterial community. A significant increase in the risk for inflammatory bowel diseases (IBDs) is associated with high cholesterol diets; dysbiosis, an imbalanced composition of gut bacteria, is an important hallmark of intestinal inflammation in patients with IBDs. However, the role of dietary cholesterol in shaping the commensal bacteria and in controlling the pathogenesis and development of IBDs has not been yet addressed at the molecular level. Using a novel in vitro tissue-engineered system, we will dissect dietary cholesterol/intestinal immune cells axis in a mechanistic fashion, uncovering the biochemical and cellular requirements for the cholesterol metabolism to locally regulate intestinal antibody secretion and shape intestinal commensal bacteria. By skewing the commensal composition in vivo with the use of antibiotics, we will model the degree of dysbiosis observed in patients with IBDs and we will reveal the molecular relationship between dietary cholesterol absorption, commensal bacteria and intestinal inflammation. Our proposed research has a high intrinsic translational value, as the identity of the commensal strains that can modulate cholesterol absorption and IgA secretion in health and disease could provide clinical alternatives to restore intestinal homeostasis through pharmacological or dietary interventions.