SRA

The perinatal period is a critical time-window in establishing T-cell tolerance. Regulatory T cells (Tregs) made during the first two weeks of life are key drivers of perinatal tolerance induction, but how these cells are generated and operate has not been established. To elucidate the unique environment murine perinatal Tregs encounter within the lymph nodes (LNs) as they first emerge from the thymus, and how it evolves over the succeeding days, we employed single-cell RNA sequencing to generate an atlas of the early LN niche. A highly dynamic picture emerged, the stromal-cell compartment showing the most striking changes and putative interactions with other LN cell compartments. In particular, LN stromal cells showed increasing potential for lymphocyte interactions with age. Analogous studies on mice lacking a:ß T cells or enriched for autoreactive a:ß T cells revealed an acute stromal-cell response to a:ß T cell dysfunction, largely reflecting dysregulation of Tregs. Punctual ablation of perinatal Tregs induced stromal-cell activation that was dependent on both interferon-gamma signaling and activation of conventional CD4+ T cells. These findings elucidate some of the earliest cellular and molecular events in perinatal induction of T-cell tolerance, providing a framework for future explorations. Overall design: Pooled inguinal, axillary, and brachial lymph nodes from day 5 and week 2 B6 mice were gently digested and flow-cytometrically purified. 500-1000 fibroblastic reticular cells, Ly6CHi monocyte-macrophages, or Ly6CLo monocyte-macrophages were doubles sorted according to the following gating strategies. FRC: CD45-,CD31-,Pdpn+Pdgfra+; monocyte-macrophages were gated as Lin(Thy1, CD3e,CD19,NK1.1,Ly6G,BST2)-, CD11b+, CD64+ cells and gated depending on Ly6CHi vs Lo expression.