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Extended report
TCR repertoire sequencing identifies synovial Treg cell clonotypes in the bloodstream during active inflammation in human arthritis
  1. Maura Rossetti1,2,3,
  2. Roberto Spreafico1,2,4,
  3. Alessandro Consolaro5,
  4. Jing Yao Leong1,
  5. Camillus Chua1,
  6. Margherita Massa6,
  7. Suzan Saidin1,
  8. Silvia Magni-Manzoni7,
  9. Thaschawee Arkachaisri8,
  10. Carol A Wallace9,
  11. Marco Gattorno5,
  12. Alberto Martini5,
  13. Daniel J Lovell10,
  14. Salvatore Albani1
  1. 1SingHealth Translational Immunology and Inflammation Centre, SingHealth and Duke-NUS Graduate Medical School, Singapore, Singapore
  2. 2Translational Research Unit, Sanford-Burnham Medical Research Institute, San Diego, California, USA
  3. 3Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, USA
  4. 4Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, California, USA
  5. 5Second Pediatrics Division, University of Genoa and G Gaslini Institute, Genova, Italy
  6. 6Lab Biotecnologie, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy
  7. 7Pediatric Rheumatology Unit, IRCCS Ospedale Pediatrico Bambino Gesù, Rome, Italy
  8. 8Duke-NUS Graduate Medical School and Rheumatology and Immunology Service, KK Women's and Children's Hospital, Singapore, Singapore
  9. 9Seattle Children's Hospital and Research Institute, Seattle, Washington, USA
  10. 10Division of Rheumatology, Cincinnati Children's Hospital Medical Center, and Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
  1. Correspondence to Dr Maura Rossetti, SingHealth Translational Immunology and Inflammation Centre, The Academia, 20 College Road, Discovery Tower Level 8, Singapore 169856, Singapore; maurarossetti{at}, mrossetti{at}


Objectives The imbalance between effector and regulatory T (Treg) cells is crucial in the pathogenesis of autoimmune arthritis. Immune responses are often investigated in the blood because of its accessibility, but circulating lymphocytes are not representative of those found in inflamed tissues. This disconnect hinders our understanding of the mechanisms underlying disease. Our goal was to identify Treg cells implicated in autoimmunity at the inflamed joints, and also readily detectable in the blood upon recirculation.

Methods We compared Treg cells of patients with juvenile idiopathic arthritis responding or not to therapy by using: (i) T cell receptor (TCR) sequencing, to identify clonotypes shared between blood and synovial fluid; (ii) FOXP3 Treg cell-specific demethylated region DNA methylation assays, to investigate their stability and (iii) flow cytometry and suppression assays to probe their tolerogenic functions.

Results We found a subset of synovial Treg cells that recirculated into the bloodstream of patients with juvenile idiopathic and adult rheumatoid arthritis. These inflammation-associated (ia)Treg cells, but not other blood Treg cells, expanded during active disease and proliferated in response to their cognate antigens. Despite the typical inflammatory-skewed balance of immune mechanisms in arthritis, iaTreg cells were stably committed to the regulatory lineage and fully suppressive. A fraction of iaTreg clonotypes were in common with pathogenic effector T cells.

Conclusions Using an innovative antigen-agnostic approach, we uncovered a population of bona fide synovial Treg cells readily accessible from the blood and selectively expanding during active disease, paving the way to non-invasive diagnostics and better understanding of the pathogenesis of autoimmunity.

  • Juvenile Idiopathic Arthritis
  • Rheumatoid Arthritis
  • Synovial fluid
  • T Cells

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See:

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