Cellular polarity asymmetrically functionalizes pathogen recognition receptor-mediated intrinsic immune response in human intestinal epithelium cells
Intestinal epithelial cells (IECs) act as a physical barrier separating the commensal-containing intestinal tract from the sterile interior. These cells have found a complex balance allowing them to be prepared for pathogen attacks while still tolerating the presence of bacteria/viral stimuli present in the lumen of the gut. Using primary human IECs, we probed the mechanisms, which allow for such a tolerance. We discovered that viral infection emanating from the basolateral side of IECs elicited a stronger intrinsic immune response as compared to lumenal apical infection. We determined that this asymmetric immune response was driven by the clathrin-sorting adapter AP-1B which mediates the polarized sorting of Toll-like receptor 3 (TLR3) toward the basolateral side of IECs. Mice and human IECs lacking AP-1B showed an exacerbated immune response following apical stimulation. Together these results suggest a model where the cellular polarity program plays an integral role in the ability of IECs to partially tolerate apical commensals while remaining fully responsive against invasive basolateral pathogens.