Human regulatory T cells locally differentiate and are functionally heterogeneous within the inflamed arthritic joint

Abstract

Objective Tregs are crucial for immune regulation, and environment‐driven adaptation of effector (e)Tregs is essential for local functioning. However, the extent of human Treg heterogeneity in inflammatory settings is unclear. Methods We combined single‐cell RNA‐ and TCR‐sequencing on Tregs derived from three to six patients with juvenile idiopathic arthritis (JIA) to investigate the functional heterogeneity of human synovial fluid (SF)‐derived Tregs from inflamed joints. Confirmation and suppressive function of the identified Treg clusters was assessed by flow cytometry. Results Four Treg clusters were identified; incoming, activated eTregs with either a dominant suppressive or cytotoxic profile, and GPR56 + CD161 + CXCL13 + Tregs. Pseudotime analysis showed differentiation towards either classical eTreg profiles or GPR56 + CD161 + CXCL13 + Tregs supported by TCR data. Despite its most differentiated phenotype, GPR56 + CD161 + CXCL13 + Tregs were shown to be suppressive. Furthermore, BATF was identified as an overarching eTreg regulator, with the novel Treg‐associated regulon BHLHE40 driving differentiation towards GPR56 + CD161 + CXCL13 + Tregs, and JAZF1 towards classical eTregs. Conclusion Our study reveals a heterogeneous population of Tregs at the site of inflammation in JIA. SF Treg differentiate to a classical eTreg profile with a more dominant suppressive or cytotoxic profile that share a similar TCR repertoire, or towards GPR56 + CD161 + CXCL13 + Tregs with a more distinct TCR repertoire. Genes characterising GPR56 + CD161 + CXCL13 + Tregs were also mirrored in other T‐cell subsets in both the tumor and the autoimmune setting. Finally, the identified key regulators driving SF Treg adaptation may be interesting targets for autoimmunity or tumor interventions.

Role of Adhesion G Protein-Coupled Receptors in Immune Dysfunction and Disorder

“…Immunoprofiling of synovial CD4 + T cells of anti-citrullinated protein antibodies (ACPA) + and ACPA − RA patients using the single cell sequencing technology identified specific GPR56 expression in the CXCL13 high peripheral helper T (T PH ) cell subset that contains most clonally expanded T cells in the inflamed joints [ 129 ]. Similar findings were reported by Lutter et al who showed that GPR56 expression defines a specific suppressive CD161 + CXCL13 + Treg cell subset in patients with juvenile idiopathic arthritis (JIA) [ 130 ].…”

T lymphocytes-related cell network in the pathogenesis of juvenile idiopathic arthritis: a key point for personalized treatment

“…However, SF Treg cells do not represent a homogeneous cell population. In agreement with the hypothesis of a selective modulation of circulating Treg phenotype following their migration into the inflamed joints, single cell RNA sequencing data demonstrated that several clusters can be identified within the population of SF Treg [26 ▪ ]. This finding reflects the phenotypic and functional heterogeneity of this cell population.…”

“…This finding reflects the phenotypic and functional heterogeneity of this cell population. Pseudotime analysis and single-cell TCR sequencing data support the concept that the distinct clusters reflect distinct developmental stages [26 ▪ ].…”

MGPfactXMBD: A Model-Based Factorization Method for scRNA Data Unveils Bifurcating Transcriptional Modules Underlying Cell Fate Determination

“…In addition, the consensus trajectory revealed new subtypes of cells demonstrating highly relevant transcriptional characteristics. Particularly, we reported new subtypes of tumor associated CD8 + T cells characterized by different TBX21 and BHLHE40 activity, both of which are known regulators of CD8 + T cell functionality(Lutter et al, 2022; Pritchard et al, 2023; Salmon et al, 2022; Trapani, 2001). These data suggest that MGPfact is capable to discover gene modules with strong and consistent transcriptional background hence better interpretability.…”