Regulatory T Cell Cd39 Expression As A Predictor Of Early Remission-Induction With Methotrexate In New-Onset Rheumatoid Arthritis

secretion by patient-derived monocytes, a mechanism with translational potential in SpA. Conclusion: Our detailed characterization of Tregs at an important inflammatory site illustrates the marked specialization of Treg subpopulations and identifies a broad transcriptional profile upregulated across all synovial regulatory cells. Our TCR analysis provides evidence of Treg clonal expansion, which may be driven by antigen, and confirms functional specialisation of individual clones. We also propose a new insight into a Treg functional mechanism through LAG-3 that suggests a novel therapeutic approach to immune-driven diseases. REFERENCES: [1] Penkava et al., Nature Communications, 2020 Disclosure of Interests: Davide Simone: None declared, Frank Penkava: None declared, Anna Ridley: None declared, Stephen Sansom: None declared, Hussein Al Mossawi Employee of: UCB, Paul Bowness Grant/research support from: Regeneron, Celgene/BMS and GSK DOI: 10.1136/annrheumdis-2021-eular.4278