Hematopoietic stem and progenitor cells integrate microbial signals to promote post‐inflammation gut tissue repair

Bone marrow (BM)-resident hematopoietic stem and progenitor cells (HSPCs) are often activated following bacterial insults to replenish the host hemato-immune system, but how they integrate the associated tissue damage signals to initiate distal tissue repair is largely unknown. Here, we show that acute gut inflammation expands HSPCs in the BM and directs them to inflamed mesenteric lymph nodes through GM-CSFR activation for further expansion and potential differentiation into Ly6C(+)/G(+) myeloid cells specialized in gut tissue repair. We identified this process to be mediated by Bacteroides, a commensal gram-negative bacteria that activates innate immune signaling. These findings establish cross-organ communication between the BM and distant inflamed sites, whereby a certain subset of multipotent progenitors is specified to respond to imminent hematopoietic demands and to alleviate inflammatory symptoms.