Abstract
Toleroge nic DCs and Tregs are believed to play a critical role in oral tolerance. However, the mechanisms of the generation of tolerogenic DCs and activation of Tregs in the gut remain poorly understood. This study aims to dissect the molecular mechanisms by which IECs and protein antigen induce functional tolerogenic DCs and Tregs. Expression of αvβ6 by gut epithelial cell-derived exosomes, its coupling with food antigen, and their relationship with the development of functional tolerogenic DCs and Tregs were examined by using in vitro and in vivo approaches. The results show that IECs up-regulated the integrin αvβ6 upon uptake of antigens. The epithelial cell-derived exosomes entrapped and transported αvβ6 and antigens to the extracellular environment. The uptake of antigens alone induced DCs to produce LTGFβ, whereas exosomes carrying αvβ6/antigen resulted in the production of abundant, active TGF-β in DCs that conferred to DCs the tolerogenic properties. Furthermore, αvβ6/OVA-carrying, exosome-primed DCs were found to promote the production of active TGF-β in Tregs. Thus, in vivo administration of αvβ6/OVA-laden exosomes induced the generation of Tregs and suppressed skewed Th2 responses toward food antigen in the intestine. Our study provides important molecular insights into the molecular mechanisms of Treg development by demonstrating an important role of IEC-derived exosomes carrying αvβ6 and food antigen in the induction of tolerogenic DCs and antigen-specific Tregs.