Neonatally imprinted mesenteric lymph node stromal cell subsets induce tolerogenic dendritic cells [endogenous FSCs]

Gut-draining mesenteric lymph nodes (mLNs) play a key role in peripheral tolerance towards food and commensal antigens by providing an optimal microenvironment for efficient de novo induction of Foxp3+ regulatory T cells (Tregs). We recently identified mLN stromal cells as critical cellular players in this process and demonstrated that their tolerogenic properties are imprinted by microbiota. Here, we show that this imprinting process already takes place in the neonatal phase and renders the mLN stromal cell compartment resistant to inflammatory perturbations later in life. Utilizing LN transplantation, RNA-seq and single-cell RNA-seq allowed identification of stably imprinted expression signatures in mLN fibroblastic stromal cells. We dissected common stromal cell subsets across gut-draining mLNs and skin-draining LNs with location-specific immunomodulatory functions, such as subset-specific expression of Aldh1a2/3. Accordingly, mLN stromal cells shaped resident dendritic cells to attain high Treg-inducing capacity in a Bmp2-dependent manner. Thus, crosstalk between mLN stromal and resident dendritic cells provides a robust feedback mechanism for the maintenance of intestinal tolerance. Identification of differentially expressed genes in fibroblastic stromal cells from mesenteric or skin-draining lymph nodes of germ-free or specific-pathogen-free housed mice.