Lymph Node Stromal Cell Responses to Perinatal T Cell Waves

Abstract

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 perinatal Tregs encounter within the lymph nodes (LNs) as they first emerge from the thymus, and how it evolves with the succeeding days, we employed single-cell RNA sequencing (scRNAseq) to generate an atlas of the early LN niche in mice. 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 α:β T cells or enriched for auto reactive α:β T cells revealed an acute stromal-cell response to α:β 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 CD4+ conventional T cells. These findings elucidate some of the earliest cellular and molecular events in perinatal induction of T-cell tolerance and provide a framework for future explorations.