Endocytic pathways of luminal antigens intersect MHC class I and class II pathways in multivesicular late endosomes – Antigen trafficking in intestinal epithelial cells studied in…

Background and Aims: In Crohn's disease (CD), intestinal epithelial cells (IEC) are suggested to be involved in the stimulation of pro-inflammatory CD4+ and CD8+ T cells. The underlying mechanisms of MHC class I and class II-associated presentation of exogenous antigens by IEC remain unknown. Here we investigate the subcellular expression of MHC class I and class II in IEC and it's interference with the endocytic trafficking of luminal antigens, in vivo. Methods: During ileocolonoscopy, ovalbumin (OVA, in saline) was sprayed onto the ileal mucosa of CD patients (active ileitis and ileitis in remission) and healt…