Dendritic cells patrol epithelium and the lumen of the crypts associated with the organized lymphoid tissue of the colon. (161.1)

Abstract

Abstract Antigen capture and presentation by the gut dendritic cells (DCs) is a complicated process that often involves a direct sampling of the antigens from the lumen. Peyer’s patches (PP) and colonic patches (CP) contain two distinct population of DCs that are thought to participate in the antigen uptake and transport of antigens from the lumen. One group of the DCs sample the lumen by extending the transepithelial dendrites from the lamina propria. The other group of DCs is localized in the intraepithelial compartment itself. In our study we have shown, by intravital imaging of the colon, that the previously reported population of intraepithelial DCs belongs to the fraction of highly motile CD11c+ cells that circulate between crypts and the T-cell and B-cell zones of the CP. We observed that these CD11c+ cells come from the T-cell zone and make a brief contact with the lumen before retreating. Upon examination of the expression profiles of different chemokines we found that CCL20 is expressed on the apical portion of the colonic patch-associated epithelial cells. Administration of anti-CCL20 antibodies blocked homing of CD11c+ cells to the intraepithelial compartment. Motile CD11c+ cells were also able to uptake fluorescent particles and Salmonella bacteria from the lumen and rapidly transport them to the T- and B-cell zones. Thus intraepithelial DCs might play an important role in antigen uptake and trafficking in the gut lymphoid compartments.