TCR repertoire sequencing identifies synovial Treg cell clonotypes in the bloodstream during active inflammation in human arthritis.
OBJECTIVE
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.
SingHealth Translational Immunology and Inflammation Centre, SingHealth and Duke-NUS Graduate Medical School, Singapore, Singapore.|Translational Research Unit, Sanford-Burnham Medical Research Institute, San Diego, California, USA.|Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, USA.
Maura
http://orcid.org/0000-0003-3347-6200
M
Rossetti
SingHealth Translational Immunology and Inflammation Centre, SingHealth and Duke-NUS Graduate Medical School, Singapore, Singapore.|Translational Research Unit, Sanford-Burnham Medical Research Institute, San Diego, California, USA.|Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, California, USA.
Roberto
R
Spreafico
Second Pediatrics Division, University of Genoa and G Gaslini Institute, Genova, Italy.
Alessandro
A
Consolaro
SingHealth Translational Immunology and Inflammation Centre, SingHealth and Duke-NUS Graduate Medical School, Singapore, Singapore.
Jing Yao
JY
Leong
SingHealth Translational Immunology and Inflammation Centre, SingHealth and Duke-NUS Graduate Medical School, Singapore, Singapore.
Camillus
C
Chua
Lab Biotecnologie, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy.
Margherita
M
Massa
SingHealth Translational Immunology and Inflammation Centre, SingHealth and Duke-NUS Graduate Medical School, Singapore, Singapore.
Suzan
S
Saidin
Pediatric Rheumatology Unit, IRCCS Ospedale Pediatrico Bambino Gesù, Rome, Italy.
Silvia
S
Magni-Manzoni
Duke-NUS Graduate Medical School and Rheumatology and Immunology Service, KK Women's and Children's Hospital, Singapore, Singapore.
Thaschawee
T
Arkachaisri
Seattle Children's Hospital and Research Institute, Seattle, Washington, USA.
Carol A
CA
Wallace
Second Pediatrics Division, University of Genoa and G Gaslini Institute, Genova, Italy.
Marco
M
Gattorno
Second Pediatrics Division, University of Genoa and G Gaslini Institute, Genova, Italy.
Alberto
A
Martini
Division of Rheumatology, Cincinnati Children's Hospital Medical Center, and Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.
Daniel J
DJ
Lovell
SingHealth Translational Immunology and Inflammation Centre, SingHealth and Duke-NUS Graduate Medical School, Singapore, Singapore.
Salvatore
S
Albani
D000293:Adolescent; D000328:Adult; D001171:Arthritis, Juvenile / Q000097:blood / Q000276:immunology*; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D019175:DNA Methylation; D005260:Female; D005434:Flow Cytometry; D019674:Genes, T-Cell Receptor beta / Q000235:genetics; D006801:Humans; D008297:Male; D011948:Receptors, Antigen, T-Cell / Q000235:genetics*; D013582:Synovial Fluid / Q000166:cytology* / Q000276:immunology; D013583:Synovial Membrane; D050378:T-Lymphocytes, Regulatory / Q000166:cytology* / Q000276:immunology; D055815:Young Adult
D011948:Receptors, Antigen, T-Cell
Juvenile Idiopathic Arthritis; Rheumatoid Arthritis; Synovial fluid; T Cells