Distinct Injury Responsive Regulatory T Cells Identified by Multi-Dimensional Phenotyping.

CD4 regulatory T cells (Tregs) activate and expand in response to different types of injuries, suggesting that they play a critical role in controlling the immune response to tissue and cell damage. This project used multi-dimensional profiling techniques to comprehensively characterize injury responsive Tregs in mice. We show that CD44 Tregs expand in response to injury and were highly suppressive when compared to CD44 Tregs. T cell receptor (TCR) repertoire analysis revealed that the CD44 Treg population undergo TCRαβ clonal expansion as well as increased TCR CDR3 diversity. Bulk RNA sequencing and single-cell RNA sequencing with paired TCR clonotype analysis identified unique differences between CD44 and CD44 Tregs and specific upregulation of genes in Tregs with expanded TCR clonotypes. Gene ontology analysis for molecular function of RNA sequencing data identified chemokine receptors and cell division as the most enriched functional terms in CD44 Tregs versus CD44 Tregs. Mass cytometry (CyTOF) analysis of Tregs from injured and uninjured mice verified protein expression of these genes on CD44 Tregs, with injury-induced increases in Helios, Galectin-3 and PYCARD expression. Taken together, these data indicate that injury triggers the expansion of a highly suppressive CD44 Treg population that is transcriptionally and phenotypically distinct from CD44 Tregs suggesting that they actively participate in controlling immune responses to injury and tissue damage.