Primary Sjögren's syndrome (pSS) is a systemic auto-immune disease typified by dryness of the mouth and eyes. A majority of patients with pSS have a type-I interferon (IFN)-signature, which is defined as the increased expression of IFN-induced genes in circulating immune cells and is associated with increased disease activity. As plasmacytoid dendritic cells (pDC) are the premier type-I IFN-producing cells and are present at the site of inflammation, they are thought to play a significant role in pSS pathogenesis. Considering the lack of data on pDC regulation and function in pSS patients, we here provided the first in-depth molecular characterization of pSS pDCs. In addition, a group of patients with non-Sjögren's sicca (nSS) was included; these poorly studied patients suffer from complaints similar to pSS patients, but are not diagnosed with Sjögren's syndrome. We isolated circulating pDCs from two independent cohorts of patients and controls (each n = 31) and performed RNA-sequencing, after which data-driven networks and modular analysis were used to identify robustly reproducible transcriptional “signatures” of differential and co-expressed genes. Four signatures were identified, including an IFN-induced gene signature and a ribosomal protein gene-signature, that indicated pDC activation. Comparison with a dataset of in vitro activated pDCs showed that pSS pDCs have higher expression of many genes also upregulated upon pDC activation. Corroborating this transcriptional profile, pSS pDCs produced higher levels of pro-inflammatory cytokines, including type-I IFN, upon in vitro stimulation with endosomal Toll-like receptor ligands. In this setting, cytokine production was associated with expression of hub-genes from the IFN-induced and ribosomal protein gene-signatures, indicating that the transcriptional profile of pSS pDCs underlies their enhanced cytokine production. In all transcriptional analyses, nSS patients formed an intermediate group in which some patients were molecularly similar to pSS patients. Furthermore, we used the identified transcriptional signatures to develop a discriminative classifier for molecular stratification of patients with sicca. Altogether, our data provide in-depth characterization of the aberrant regulation of pDCs from patients with nSS and pSS and substantiate their perceived role in the immunopathology of pSS, supporting studies that target pDCs, type-I IFNs, or IFN-signaling in pSS.

No abstract

No abstract

Objective: Effective treatment for primary Sjögren's syndrome (pSS) is not available. pSS immunopathology involves a variety of immune-cells and dysregulated pathways; targeting several pathways instead of only one could therefore be effective. Treatment with leflunomide (LEF) and hydroxychloroquine (HCQ) might be successful given their unique immunosuppressive properties. We aimed to study the in vitro effects of LEF, HCQ and their combination on T-and B-cell proliferation, cytokine and immunoglobulin production by activated PBMCs. Methods: PBMCs of six healthy individuals and nine pSS patients were stimulated with superantigen and TLR9 agonist to mimic the hallmark features. LEF, HCQ and their combinations were tested at clinically observed concentrations and proliferation, cytokine and immunoglobulin production were measured. Results: TCR/TLR9 activation of PBMCs induced strong proliferation of T and B-cells and production of CXCL13, IFN-α, IFN-γ, IgG and IgM. LEF dose-dependently inhibited all measured parameters, where HCQ potently and dose-dependently decreased B cell proliferation, CXCL13, IFN-α, IgG and IgM production. At different concentration combinations, HCQ and LEF inhibited several immune hallmark features more potently than each single compound. Conclusion: A combination of LEF and HCQ at clinically applicable concentrations additively inhibits immune activation, supporting a potential implementation of this drug combination in pSS treatment.

No abstract

Primary Sjögren's syndrome (pSS) is an auto immune disorder characterized by exocrine dysfunction as a result of chronic inflammation of the glands. Part of the patients also develops inflammation in other organs. In a complex interplay of different cell types such as T-cells, B-cells, dendritic cells, monocytes/macrophages and NK cells and their effector molecules, all contribute to one of the ultimate hallmarks of pSS: B-cell hyperactivity, subsequent autoantibody production and eventually formation of germinal center-like structures in the salivary gland. Effective treatment options for this disease are currently lacking. Biological DMARDs (bDMARDs) including those targeting B-cells or B-cell activation (directly or indirectly) have been studied, so far with limited efficacy. Besides that, their high costs provide a major drawback for implementation. Relatively inexpensive conventional DMARDs (cDMARDs) with well-known safety profiles have been shown efficacious in numerous clinical studies in multiple (rheumatic) diseases. cDMARDs target several pathways that are crucial in pSS immunopathology and some have proven to effectively inhibit B-cell hyperactivity and immune activation when given to patients. However, strong conclusions about potential efficacy are hampered by lack of standardization of inclusion criteria and outcome measures, dosing and validated biomarkers for patient selection. Proper implementation of these could help to optimize the use of cDMARDs in pSS treatment. In analogy with effective treatment strategies in for example rheumatoid arthritis, combination of two cDMARDs targeting different dysregulated pathwaysmight result in additive or synergistic inhibition of immune activation. In view of this and the unique and potent mechanisms of action to target immunopathology in pSS, optimizing cDMARDs for treatment of pSS is worthwhile.