Antigen targeting to MHC class II-enriched compartments in colonic epithelial cells of Crohn's disease patients

Background & Aims: In Crohn's disease (CD), colonic epithelial cells (CECs) are suggested to stimulate pro-inflammatory CD4+ T cells. The endocytic pathways of lumenal antigens, involved in underlying MHC class II presentation by CECs, remain to be defined. Our aim was to elucidate antigen trafficking and associated MHC class II expression in CECs of CD patients in vivo. Methods: In patients with CD and healthy controls undergoing colonoscopy, ovalbumin (OVA)(150mg/mL in saline; 10mL) was sprayed directly onto inflamed or normal mucosa. Mucosal biopsies were taken before and 5, 10 and 20minutes after OVA exposur…