Specificity and Diversity of the Mouse Peyer's Patch Mononuclear Phagocyte System

Peyer’s patches (PP) are primary inductive sites of mucosal immunity. Defining PP mononuclear phagocyte system is crucial to understand the initiation of mucosal immune response. Although several mouse Peyer’s patch dendritic cell (DC) subsets have been described in the literature, to our knowledge nothing is known about the macrophage diversity in PP. Here, we succeeded in distinguishing conventional DC, monocyte-derived DC and macrophage subsets of mouse PP. We defined their phenotype, distribution, origin, lifespan and transcriptional profiles. We show that monocytes differentiate locally into cells that display the characteristics of macrophages, i.e. long-lived cells with strong phagocytic activity but poor naïve T cell priming ability. However, these PP macrophages do not express classic intestinal macrophage markers which may explain their poor characterization so far. Interestingly, monocytes can also give rise in the same location to lysozyme-expressing DC (LysoDC) which, unlike macrophages, display a rapid renewal rate and strongly express genes of the MHCII presentation pathway.