(255) Functional and dysfunctional T regulatory cell states in human tissues in RA and other autoimmune arthritic diseases

Introduction/Rationale: Regulatory T cells (Tregs), characterized by FOXP3 expression, are essential for maintaining immune homeostasis by controlling inflammation. However, in autoimmune diseases such as rheumatoid arthritis (RA), impaired Treg function contributes to immune dysregulation and disease pathology. The phenotype of impaired Treg function in RA and other autoimmune diseases remains unknown.

Methods: We employed unbiased paired single cell RNA-sequencing (scRNAseq) and T cell receptor (TCR)-seq analysis of Tregs from synovial tissue, synovial fluid, and blood from 79 RA patients and blood from 5 healthy donors in an integrated analysis. We mapped Tregs from additional inflammatory arthritic conditions, Juvenile Idiopathic Arthritis (JIA) and Psoriatic Arthritis (PsA), to evaluate the Treg heterogeneity across different conditions.

Results: We identified two predominant Treg states, CD25hiCXCR6pos Tregs with strong suppressive function, and CD25loAREGpos Tregs, a dysfunctional state exclusively enriched in synovial tissues but not in blood. Highly suppressive, CD25hi Tregs presented dynamic differentiation potential through high shared clones across different clusters. Computational and in vitro analyses revealed that cortisol induced AREG expression, suppressed glycolysis, and impaired the suppressive function of CD25loAREGpos Tregs. In contrast, CD25hiCXCR6pos Tregs were highly suppressive and showed coordinated abundance with macrophages in synovial tissue which promoted their functional suppressive state through membrane-bound TNFα signaling. These two Treg subsets were similarly found in the synovial tissue in JIA, indicating conserved mechanisms across arthritic diseases.

Conclusion: Together, our findings define distinct pathways driving divergent functional and dysfunctional Treg states in inflamed tissues and point to interventions that may prevent or reverse the development of the dysfunctional state.