Date: Sunday, November 8, 2020
Session Type: Poster Session C
Session Time: 9:00AM-11:00AM
Background/Purpose: Rheumatoid arthritis (RA) often has a progressive and debilitating course, with significant impact on the patient’s quality of life. Despite the long-known association with autoantibodies, knowledge of the role of B cells and their potential direct contribution to RA pathogenesis remains elusive.
Characterization of B cell subpopulations in the periphery and synovial tissue.
Identification of chemokine receptors responsible for the synovial accumulation of B cells.
Characterization of B cell function and metabolism under the hypoxic conditions of the RA joint.
Methods: Synovial tissue biopsies from RA patients were obtained through key-hole arthroscopy followed by single cell flow cytometric analysis of B cell subpopulations and chemokine receptor expression. SPICE analysis was performed for the chemokine receptor expression of synovial B cells and B cell invasion assays. Functional characterization of sorted RA B cells, cultured in vitro under hypoxia, simulating the inflamed joint environment. Characterization of B cell metabolism and transcriptional regulation of pSTAT3 by flow cytometry. Notably, novel, non-invasive Fluorescent Lifetime Imaging Microscopy (FLIM) assay for the characterisation of the metabolic status of sorted RA patient PD-1 B cells coupled with RNAseq analysis was performed.
Results: Extensive flow-cytometric characterisation and SPICE algorithm analyses of single-cell synovial tissue from RA-patients revealed the accumulation of switched and double negative memory PD-1 expressing B cells at the site of inflammation. Accumulation of memory B cells is mediated by CXCR3, evident by the observed increase in CXCR3 expressing synovial B cells compared to the periphery, differential regulation by key synovial cytokines, and restricted B cell invasion demonstrated in response to CXCR3 blockade. Notably, under 3% O2 hypoxic conditions that mimic the joint-microenvironment, RA B cells maintain marked expression of MMP-9,-TNF and IL-6, with PD-1+ B-cells demonstrating higher expression of CXCR3, CD80, CD86, IL-1β and GMCSF than their PD-1– counterparts. Following functional analysis and flow cell sorting of RA PD-1+ vs PD-1– B-cells, we demonstrate using RNAseq and novel FLIM visualisation of cellular NADH, a significant shift in metabolism of RA PD-1+ B-cells towards glycolysis, associated with an increased transcriptional signature of key cytokines and chemokines that are strongly implicated in RA pathogenesis.
Conclusion: Highly polyfunctional pro-inflammatory T cell responses pre-date disease onset as demonstrated by the accumulation of polyfunctional T cells in the synovial tissue of pre-RA arthralgia subjects. These data highlight a key early pathogenic role for T cell plasticity and specific synovial T cell clusters including, DP T cells in RA.
To cite this abstract in AMA style:Floudas A, Neto N, Marzaioli V, Murray K, Moran B, Monaghan M, Low C, Mullan R, Rao N, Krishna V, Nagpal S, Veale D, Fearon U. Pathogenic, Glycolytic PD-1+ B Cells Accumulate in the Hypoxic RA Joint [abstract]. Arthritis Rheumatol. 2020; 72 (suppl 10). https://acrabstracts.org/abstract/pathogenic-glycolytic-pd-1-b-cells-accumulate-in-the-hypoxic-ra-joint/. Accessed January 19, 2022.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/pathogenic-glycolytic-pd-1-b-cells-accumulate-in-the-hypoxic-ra-joint/