Pyruvate-GPR31 axis induces LysoDC dendrite protrusion to M-cell pockets for effective immune responses.

Peyer's patches (PPs) are sites of antigen entry and immunoinduction in the small intestine. In PPs, pathogens are transferred through microfold (M) cells; however, the mechanisms of antigen capture by mononuclear phagocytes beneath M cells remain unclear. Here, we demonstrate that bacterial metabolite pyruvate acted on lysozyme-expressing dendritic cells (LysoDCs), a monocyte-derived phagocyte subset, and induced protrusion of dendrites particularly with "balloon" shapes into basolateral M-cell pockets via its receptor, G-protein coupled receptor 31 (GPR31). Pyruvate administration in wild-type but not -deficient mice increased LysoDC uptake of orally infected . GPR31 signaling boosted antigen processing and altered gene expression. It also increased LysoDC migration to the interfollicular region, thereby promoting production of pathogen-specific Th1 cells as well as cytotoxic T cells, and effector T cell migration to the lamina propria. Furthermore, oral pyruvate administration conferred high resistance to a virulent strain in a GPR31-dependent manner. Collectively, the pyruvate - GPR31 axis plays critical roles in orchestrating intestinal protective immunity.