Session Type: Abstract Session
Session Time: 3:00PM-3:50PM
Background/Purpose: Clonal T cell expansions – some large – have been identified in the peripheral blood (PB) and in synovial tissue (ST) of multiple joints from recently-diagnosed rheumatoid arthritis (RA) patients. As the degree of ST clonal dominance decreased with longer disease duration, new-onset RA presents the ideal opportunity to study the transcriptome and TCRα/β of individual clonotypes. This can be achieved using single-cell RNA-sequencing, which already identified novel T cell subsets in longstanding RA. To elucidate the TCR usage and transcriptome of oligoclonally expanded T cells in the PB and ST compartments in newly-diagnosed RA, we combined TCR repertoire, clonality and transcriptomic analysis of individual ST and paired PB mononuclear cells (PBMC) in untreated HLA-DRB1*0401+ ACPA+ RA patients.
Methods: PBMC and whole cryopreserved ST samples were collected from 4 treatment-naïve RA patients undergoing arthroscopic synovial biopsy. CD45+ leukocytes from cryopreserved PBMC, and CD45+ leukocytes and CD45– fibroblasts isolated from paired disaggregated ST, by fluorescence-activated cell sorting, were sequenced using 5’ RNA/TCR single-cell 10x Genomics kits. Single-cell transcriptomic analysis, using the Seurat package in R, reconstructed the compartment-specific composition of PB and ST.
Results: Myeloid cells were expanded in the ST relative to PB. Myeloid and NK cell expansion was related to arthroscopic synovitis severity. NK and B cell clusters were proportionately smaller among ST than PB leukocytes. Transcriptomics identified 10 unique CD3+TCR+ populations in PB and ST, including cytotoxic, helper and regulatory T cells. In PB, the most expanded clonotypes were CD8+ and CD4+ cytotoxic T cells. ST expanded clonotypes included CD8+ and CD4+ T cells expressing cytotoxic and multiple cytokine genes, CD4+ICOS+ T cells with evidence of IL-6 signalling, and CD4+GATA3+ tissue-resident T cells. Shared ST and PB T cell clonotypes were predominantly cytotoxic polyfunctional CD8+ T cells. A proportion of PB cytotoxic clonotypes matched known EBV and CMV-reactive clones, and a proportion of shared PB/ST cytotoxic clonotypes matched CMV-reactive clones.
Conclusion: Similar T cell clusters were identified in ST and PB. Transcriptomes of non-cytotoxic expanded CD4+ T cell clonotypes in the ST of untreated patients suggest B cell interaction and help. The most expanded clonotypes in circulation include T cells with cytotoxic and proinflammatory capability, including known viral-specific clones, some of which reach and expand in RA ST. Antigen derived and presented from persistent viruses may expand responsive clones to be bystander drivers of synovial inflammation.
To cite this abstract in AMA style:Wehr P, Nel H, Zhou C, Mehdi A, Christ A, Weedon H, Wechalekar M, Thomas R. Mapping Oligoclonally Expanded T Cells Within the Peripheral and Synovial Immune Landscape of Untreated ACPA+ Rheumatoid Arthritis Patients at the Single Cell Level [abstract]. Arthritis Rheumatol. 2020; 72 (suppl 10). https://acrabstracts.org/abstract/mapping-oligoclonally-expanded-t-cells-within-the-peripheral-and-synovial-immune-landscape-of-untreated-acpa-rheumatoid-arthritis-patients-at-the-single-cell-level/. Accessed November 25, 2020.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/mapping-oligoclonally-expanded-t-cells-within-the-peripheral-and-synovial-immune-landscape-of-untreated-acpa-rheumatoid-arthritis-patients-at-the-single-cell-level/