Intestinal epithelial cells secrete exosome-like vesicles

Background & Aims: Given the observations that intestinal epithelial cells (IECs) can present antigens to CD4(+) T lymphocytes and that professional a ntigen-presenting cells secrete exosomes (antigen-presenting vesicles), we hypothesized that IECs may secrete exosomes carrying molecules implicated i n antigen presentation, which may be able to cross the basement membrane an d convey immune information to noncontiguous immune cells. Methods: Human I EC lines HT29-19A and T84-DRB1*0401/CIITA were grown on microporous filters . Release of exosomes under basal or inflammatory conditions was evaluated in conditioned apical and basolateral media after differential ultracentrif ugations. Morphologic and biochemical characterization of exosomes was perf ormed using immunoelectron microscopy, Western blotting, and matrix-assiste d laser desorption ionization-time of flight mass spectrometry. Results : T he intestinal cell lines released 30-90-nm-diameter vesicles from the apica l and basolateral sides, and this release was significantly increased in th e presence of interferon gamma. MHC class I, MHC class II, CD63, CD26/dipep tidyl-peptidase IV, and A33 antigen were present in epithelial-derived exos omes. Conclusions: Human IEC lines secrete exosomes bearing accessory molec ules that may be involved in antigen presentation. These data are consisten t with a model in which IECs may influence antigen presentation in the muco sal or systemic immune system independent of direct cellular contact with e ffector cells.