Dendritic cells shuttle microbes across gut epithelial monolayers.

Understanding the mechanisms governing the type of induced immune response after microbial invasion, could be of crucial importance for the rational design of a bacteria-based vaccine. Targeting a vaccine directly to dendritic cells (DCs), which are considered the most powerful antigen presenting cells, could be extremely effective. Here we describe that CD11b+CD8alpha- dendritic cells are involved in the direct bacterial uptake across mucosal surfaces. DCs are widely spread in the lamina propria of the gut and are recruited at the site of infection. DCs open the tight junctions between epithelial cells, send dendrites outside of the epithelium and sample bacteria. Moreover, the integrity of the epithelial barrier is preserved because DCs express tight junction proteins, such as occludin, claudin 1 and Junctional Adhesion Molecule (JAM) and can establish tight junctions-like structures with neighbouring epithelial cells.