Immunosensing environmental information by mouse vibrissae

Immune sensing of the animal’s environment is usually viewed in the context of identifying infectious microbes, including in mucosal tissues such as intestine and lungs, where the lumen is topologically external to the animal. At these boundary surfaces, monitoring is effectively mediated by a structure comprised of specialized epithelial cells called M cells capturing microparticles such as viruses and bacteria from the luminal surface and transferring to subepithelial Dendritic Cell. This mucosal immunosensory unit efficiently gathers information (antigens, microbes) from the external environment and presents it to organized immune tissue that subsequently generates an appropriate immune response. We have now identified an unusual population of M-like cells in the isthmus of mouse vibrissae/whiskers, in a basket-type arrangement surrounding the shaft of the whisker. This layer is surrounded by an array of dendritic cells, and further surrounded by an outer layer of somatosensory nerves. The topology of these cell layers is reminiscent of intestinal Peyer’s patch but with somatosensory nerves in place of the mucosal lymphoid tissues. Our working hypothesis is that the monitoring and surveillance function associated with M-like cells is a component of a novel “immunosensory unit” communicating environmental innate immune ligand information to the somatosensory system. In this proposal we will (1) perform a detailed anatomic analysis of the relationships between the cells in this whisker structure, (2) identify the signaling mechanisms between the M-like cells, dendritic cells, and somatosensory neurons, and (3) determine how this signaling may parallel or augment the signaling of mechanosensory information by the whiskers to the central nervous system.