Background/Purpose: Arthritis is a common clinical feature of systemic lupus erythematosus (SLE), that can be present either at the onset or in later disease course. SLE-related arthritis is usually non-erosive and non-deforming as opposed to rheumatoid arthritis (RA). While RA synovial pathology has been extensively studied, little is known about the pathophysiology of arthritis in SLE. Here, we aimed to explore the cytokine and cellular compartments in synovial fluids (SF) of SLE patients with arthritic manifestations.

Methods: Paired synovial fluid mononuclear cells (SFMC) from large joint aspiration and peripheral blood samples (PBMC) from three SLE patients were analyzed by three different lineage-specific multicolor flow cytometry panels for B cells and T cells (cytotoxic and helper). SLE-derived SFMCs were further stimulated in vitro to measure T cell production of IFN gamma and IL-17. Since the majority of SF samples from SLE patients were not cellular, we analyzed the acellular SF samples (n=19) with cytokine bead array for Th1, Th17 and Th2 associated cytokines (BD Bioscience). The patients fulfilled the ACR 1982 classification criteria for SLE. Clinical records were reviewed in order to exclude the presence of comorbidities such osteoarthritis or overlap with RA.

Results: The overall frequency of CD4+ and CD8+ T cells among CD3+ T cells was similar across SFMC and PBMC samples, while CD19+ cells (B-lymphocytes) were scarcely present in the joint of SLE patients as opposed to the peripheral blood. In SF, we could identify an increased frequency of CCR6+ cells among CD4+ T cells, a marker associated with Th17 cells. IL-17-production could be validated in the (CD4+CCR6+) compartment following in vitro stimulation of SFMCs. Also, a strong IFN gamma production was seen, which may originate from the increased frequency of cytotoxic EOMES+ Granzyme A+ T cells that were also recorded in the SLE-SFMC. IFN gamma was not found in the acellular synovial fluid samples, while the TH17-associated cytokines IL-17 and IL-6 were abundant.

Conclusion: Although SLE is usually considered to be a B-cell driven disease, its common clinical features like arthritis could be driven in situ by T cells, namely TH17 cells and CD4+ T cells with cytotoxic profile.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/large-joint-arthritis-in-systemic-lupus-erythematosus-is-characterized-by-th17-cells-rather-than-b-cell-accumulation/