INNATE and ADAPTATIVE IMMUNE FUNCTIONS of PEYER'S PATCH MONOCYTE-DERIVED CELLS

Peyer's patches of the small intestine are antigen sampling and inductive sites for the establishment of mucosal immunity. They comprise clustered domes formed by B-cell follicles separated from each other by interfollicular regions enriched in T cells. The follicle-associated epithelium contains specialized epithelial cells, called M cells that bind and rapidly transport microorganisms from the lumen to the subepithelial dome (SED). The SED contains macrophages and dendritic cells (DC) among which we recently described a myeloid DC subset called LysoDC, which highly expresses the bactericidal agent lysozyme. Antigen uptake, degradation and presentation by these mononuclear phagocytes are crucial steps to induce the mucosal immune response. Here, we show that LysoDC and SED macrophages are both involved in particulate antigen uptake, display strong innate antiviral and antibacterial gene signatures and, upon TLR7 stimulation, secrete IL-6 and TNF but no IL-10 or IFNg. However, unlike macrophages, LysoDC display a rapid renewal rate, strongly express genes of the MHCII presentation pathway and efficiently prime naïve helper T cells for IFNg production.