Salivary gland epithelial cells from patients with Sjögren’s syndrome induce B-lymphocyte survival and activation

Abstract

ObjectivePrimary Sjögren's syndrome (pSS) is characterised by chronic hyperactivation of B lymphocytes. Salivary gland epithelial cells (SGECs) could play a role in promoting B-lymphocyte activation within the target tissue. We aimed to study the interactions between SGECs from patients with pSS or controls and B lymphocytes.MethodsPatients had pSS according to 2016 European League Against Rheumatism/American College of Rheumatology criteria. Gene expression analysis of SGECs and B lymphocytes from pSS and controls isolated from salivary gland biopsies and blood was performed by RNA-seq. SGECs from pSS and controls were cocultured with B-lymphocytes sorted from healthy donor blood and were stimulated. Transwell and inhibition experiments were performed.ResultsGene expression analysis of SGECs identified an upregulation of interferon signalling pathway and genes involved in immune responses (HLA-DRA, IL-7 and B-cell activating factor receptor) in pSS. Activation genes CD40 and CD48 were upregulated in salivary gland sorted B lymphocytes from patients with pSS. SGECs induced an increase in B-lymphocyte survival, which was higher for SGECs from patients with pSS than controls. Moreover, when stimulated with poly(I:C), SGECs from patients with pSS induced higher activation of B-lymphocytes than those from controls. This effect depended on soluble factors. Inhibition with anti-B-cell activating factor, anti-A proliferation-inducing ligand, anti-interleukin-6-R antibodies, JAK1/3 inhibitor or hydroxychloroquine had no effect, conversely to leflunomide, Bruton's tyrosine kinase (BTK) or phosphatidyl-inositol 3-kinase (PI3K) inhibitors.ConclusionsSGECs from patients with pSS had better ability than those from controls to induce survival and activation of B lymphocytes. Targeting a single cytokine did not inhibit this effect, whereas leflunomide, BTK or PI3K inhibitors partially decreased B-lymphocyte viability in this model. This gives indications for future therapeutic options in pSS.

The Imbalance of Circulating Follicular T Helper Cell Subsets in Primary Sjögren’s Syndrome Associates With Serological Alterations and Abnormal B-Cell Distribution

“…The upregulation of adhesion and chemokine molecules, along with metabolic stress induced apoptosis initiates the recruitment of innate immune cells and triggers an interferon-related inflammatory cascade ( 1 ). Type I interferon production by plasmacytoid dendritic cells induces infiltrating leukocytes and epithelial cells to secrete B-cell activating factor (BAFF), which promotes B-cell survival and not only contributes to B-cell hyperactivity, but also acts as a mediator between innate and adaptive immunity ( 2 , 3 ). Local accumulation and sustained survival of autoreactive B cells promote the development of ectopic germinal centers (GCs), which establish the perfect niche for autoantibody production or lymphomagenesis ( 4 , 5 ).…”

Interleukin‐7/Interferon Axis Drives T Cell and Salivary Gland Epithelial Cell Interactions in Sjögren’s Syndrome

“…We previously showed that SGECs sorted from primary SS and control SGs expressed IL7 RNA and that this expression was higher in SGECs from patients with primary SS than from controls (25). Given this finding, we hypothesized that SGECs could be a source of IL‐7 in primary SS.…”

Making Sense of Intracellular Nucleic Acid Sensing in Type I Interferon Activation in Sjögren’s Syndrome

“…Transcriptomic analyses on pSS salivary glands have revealed upregulated ISG transcripts in whole salivary gland biopsies [ 47 , 48 , 49 , 50 ] and epithelium-enriched fractions [ 51 , 52 ]. Protein expression of type I [ 14 , 53 , 54 ], type II [ 55 , 56 ], and type III IFNs [ 57 , 58 ] has been observed in salivary glands.…”

“…Transcriptomic analyses of pSS-derived salivary gland have repeatedly found upregulation of multiple ISGs involved in cytosolic RNA-sensing pathways or type I IFN signaling [ 47 , 48 , 49 , 50 , 114 , 115 , 116 ]. These findings were most pronounced in salivary glands with extensive mononuclear cell infiltrates [ 50 , 51 , 52 , 114 , 117 ]. Prominent staining of RIG-I and MDA5 has primarily been observed in infiltrating immune cells [ 64 ], which may be a reflection of localized IFN production.…”