Dynamic Surface Expression of CD103 on Human Dendritic Cells Due to Endosomal Recycling

CD103 (αE integrin) is expressed by the majority of murine intestinal dendritic cells (DCs), whereas CD103 expression by human DCs is more variable.  Specifically, CD103 by human gastric DCs was extremely low, as our recent study revealed.  Since integrins may undergo recirculation through endosomal pathways, we asked whether human DCs contained intracellular pools of CD103 that recycle through the cell membrane.  Indeed, intracellular expression of CD103 was detected in 53±12% of gastric and 73±9% of MoDCs, whereas surface expression was significantly lower, at 13±2% and 8±3%, respectively.  These data were confirmed by imaging flow cytometry and confocal microscopy, which revealed endosomal intracellular staining patterns for CD103 in both gastric DCs and MoDCs.  Furthermore, MoDCs incubated with fluorescent labelled anti-CD103 accumulated fluorescence over time, indicating endosomal recycling.  Similar results were obtained for β7, which forms the functional αEβ7 integrin heterodimer with CD103.  αEβ7 recycling through the DC membrane may enable dynamic interactions between human mucosal DCs and E-cadherin expressed by mucosal epithelia, allowing efficient DC immunosurveillance of the epithelial barrier.