Salivary gland secretome: a novel tool towards molecular stratification of patients with primary Sjögren's syndrome and non-autoimmune sicca

Salivary gland biopsy as a prognostic tool in Sjögren's syndrome

INTRODUCTION

Primary Sjögren's syndrome (pSS) is an autoimmune disorder primarily affecting salivary and lacrimal glands, although about 40% of patients experience systemic complications. In this setting, the identification of patient phenotypes characterized by increased risk of extra-glandular involvement still represents an unmet need.

AREAS COVERED

The aim of this paper is to review the scientific evidence on the utility of salivary gland biopsies in pSS, emphasizing their role in defining prognosis. In latest years, research focused on disease-specific clinical, serological, or histological features able to categorize patient prognosis. Among histopathological features, focus score and ectopic germinal centers exhibit associations with glandular and extraglandular manifestations, including higher rates of lymphomagenesis.

EXPERT OPINION

Pathological characterization of salivary glands provides information that go beyond a mere diagnostic or classification utility, providing insights for a stratification of disease severity and for predicting systemic manifestations. Thus, a salivary gland biopsy should be offered to all patients and included in routine practice, even when not strictly required for diagnostic purposes. More advanced analysis techniques of the tissue, including immunohistochemistry and 'omics' should be further explored in longitudinal studies to boost the ability to further stratify and predict disease evolution.

Precision medicine in Sjögren's disease

Sjögren's disease is a clinically and pathophysiologically heterogeneous disease to which precision medicine, on the basis of clinical and biological heterogeneity, has been not always applicable. In patients with Sjögren's disease, the relationship between dysregulated biological pathways and symptoms such as fatigue and pain or clinical manifestations is often difficult to establish. This clinical and biological dissociation also poses challenges when defining appropriate clinical endpoints for clinical trials. In the last few years, however, research efforts have been focused on gaining a better understanding of the considerable heterogeneity of Sjögren's disease by developing stratification models aimed at clustering patients with this condition into homogenous subgroups characterised by distinctive molecular signatures, biomarkers, clinical features, and outcomes. In this Review, we discuss current evidence regarding clinical, laboratory, histological, and biomolecular stratification in Sjögren's disease and examine how available stratification data can guide precision medicine and inform the design of future clinical trials.

Examining the biological pathways underlying clinical heterogeneity in Sjogren's syndrome: proteomic and network analysis

OBJECTIVES

Stratification approaches are vital to address clinical heterogeneity in Sjogren's syndrome (SS). We previously described that the Newcastle Sjogren's Stratification Tool (NSST) identified four distinct clinical subtypes of SS. We performed proteomic and network analysis to analyse the underlying pathobiology and highlight potential therapeutic targets for different SS subtypes.

METHOD

We profiled serum proteins using O-link technology of 180 SS subjects. We used 5 O-link proteomics panels which included a total of 454 unique proteins. Network reconstruction was performed using the ARACNE algorithm, with differential expression estimates overlaid on these networks to reveal the key subnetworks of differential expression. Furthermore, data from a phase III trial of tocilizumab in SS were reanalysed by stratifying patients at baseline using NSST.

RESULTS

Our analysis highlights differential expression of chemokines, cytokines and the major autoantigen TRIM21 between the SS subtypes. Furthermore, we observe differential expression of several transcription factors associated with energy metabolism and redox balance namely APE1/Ref-1, FOXO1, TIGAR and BACH1. The differentially expressed proteins were inter-related in our network analysis, supporting the concept that distinct molecular networks underlie the clinical subtypes of SS. Stratification of patients at baseline using NSST revealed improvement of fatigue score only in the subtype expressing the highest levels of serum IL-6.

CONCLUSIONS

Our data provide clues to the pathways contributing to the glandular and non-glandular manifestations of SS and to potential therapeutic targets for different SS subtypes. In addition, our analysis highlights the need for further exploration of altered metabolism and mitochondrial dysfunction in the context of SS subtypes.

Leflunomide/hydroxychloroquine combination therapy targets type I IFN-associated proteins in patients with Sjögren's syndrome that show potential to predict and monitor clinical response

OBJECTIVES

To assess to what extent leflunomide (LEF) and hydroxychloroquine (HCQ) therapy in patients with primary Sjögren's syndrome (RepurpSS-I) targets type I IFN-associated responses and to study the potential of several interferon associated RNA-based and protein-based biomarkers to predict and monitor treatment.

METHODS

In 21 patients treated with LEF/HCQ and 8 patients treated with placebo, blood was drawn at baseline, 8, 16 and 24 weeks. IFN-signatures based on RNA expression of five IFN-associated genes were quantified in circulating mononuclear cells and in whole blood. MxA protein levels were measured in whole blood, and protein levels of CXCL10 and Galectin-9 were quantified in serum. Differences between responders and non-responders were assessed and receiver operating characteristic analysis was used to determine the capacity of baseline expression and early changes (after 8 weeks of treatment) in biomarkers to predict treatment response at the clinical endpoint.

RESULTS

IFN-signatures in peripheral blood mononuclear cell and whole blood decreased after 24 weeks of LEF/HCQ treatment, however, changes in IFN signatures only poorly correlated with changes in disease activity. In contrast to baseline IFN signatures, baseline protein concentrations of galectin-9 and decreases in circulating MxA and Galectin-9 were robustly associated with clinical response. Early changes in serum Galectin-9 best predicted clinical response at 24 weeks (area under the curve 0.90).

CONCLUSIONS

LEF/HCQ combination therapy targets type-I IFN-associated proteins that are associated with strongly decreased B cell hyperactivity and disease activity. IFN-associated Galectin-9 is a promising biomarker for treatment prediction and monitoring in pSS patients treated with LEF/HCQ.

CCR9/CXCR5 Co-Expressing CD4 T Cells Are Increased in Primary Sjögren's Syndrome and Are Enriched in PD-1/ICOS-Expressing Effector T Cells

Primary Sjögren's syndrome (pSS) is an autoimmune disease characterised by B cell hyperactivity. CXCR5+ follicular helper T cells (Tfh), CXCR5-PD-1hi peripheral helper T cells (Tph) and CCR9+ Tfh-like cells have been implicated in driving B cell hyperactivity in pSS; however, their potential overlap has not been evaluated. Our aim was to study the overlap between the two CXCR5- cell subsets and to study their PD-1/ICOS expression compared to "true" CXCR5/PD-1/ICOS-expressing Tfh cells. CXCR5- Tph and CCR9+ Tfh-like cell populations from peripheral blood mononuclear cells of pSS patients and healthy controls (HC) were compared using flow cytometry. PD-1/ICOS expression from these cell subsets was compared to each other and to CXCR5+ Tfh cells, taking into account their differentiation status. CXCR5- Tph cells and CCR9+ Tfh-like cells, both in pSS patients and HC, showed limited overlap. PD-1/ICOS expression was higher in memory cells expressing CXCR5 or CCR9. However, the highest expression was found in CXCR5/CCR9 co-expressing T cells, which are enriched in the circulation of pSS patients. CXCR5- Tph and CCR9+ Tfh-like cells are two distinct cell populations that both are enriched in pSS patients and can drive B cell hyperactivity in pSS. The known upregulated expression of CCL25 and CXCL13, ligands of CCR9 and CXCR5, at pSS inflammatory sites suggests concerted action to facilitate the migration of CXCR5+CCR9+ T cells, which are characterised by the highest frequencies of PD-1/ICOS-positive cells. Hence, these co-expressing effector T cells may significantly contribute to the ongoing immune responses in pSS.

An immuno-lipidomic signature revealed by metabolomic and machine-learning approaches in labial salivary gland to diagnose primary Sjögren's syndrome

Introduction

Assessing labial salivary gland exocrinopathy is a cornerstone in primary Sjögren's syndrome. Currently this relies on the histopathologic diagnosis of focal lymphocytic sialadenitis and computing a focus score by counting lym=phocyte foci. However, those lesions represent advanced stages of primary Sjögren's syndrome, although earlier recognition of primary Sjögren's syndrome and its effective treatment could prevent irreversible damage to labial salivary gland. This study aimed at finding early biomarkers of primary Sjögren's syndrome in labial salivary gland combining metabolomics and machine-learning approaches.

Methods

We used a standardized targeted metabolomic approach involving high performance liquid chromatography coupled with mass spectrometry among newly diagnosed primary Sjögren's syndrome (n=40) and non- primary Sjögren's syndrome sicca (n=40) participants in a prospective cohort. A metabolic signature predictive of primary Sjögren's syndrome status was explored using linear (logistic regression with elastic-net regularization) and non-linear (random forests) machine learning architectures, after splitting the data set into training, validation, and test sets.

Results

Among 126 metabolites accurately measured, we identified a discriminant signature composed of six metabolites with robust performances (ROC-AUC = 0.86) for predicting primary Sjögren's syndrome status. This signature included the well-known immune-metabolite kynurenine and five phospholipids (LysoPC C28:0; PCaa C26:0; PCaaC30:2; PCae C30:1, and PCaeC30:2). It was split into two main components: the first including the phospholipids was related to the intensity of lymphocytic infiltrates in salivary glands, while the second represented by kynurenine was independently associated with the presence of anti-SSA antibodies in participant serum.

Conclusion

Our results reveal an immuno-lipidomic signature in labial salivary gland that accurately distinguishes early primary Sjögren's syndrome from other causes of sicca symptoms.

In patients with primary Sjögren's syndrome innate-like MAIT cells display upregulated IL-7R, IFN-γ, and IL-21 expression and have increased proportions of CCR9 and CXCR5-expressing cells

Introduction

Mucosal-associated invariant T (MAIT) cells might play a role in B cell hyperactivity and local inflammation in primary Sjögren's syndrome (pSS), just like previously studied mucosa-associated CCR9+ and CXCR5+ T helper cells. Here, we investigated expression of CCR9, CXCR5, IL-18R and IL-7R on MAIT cells in pSS, and assessed the capacity of DMARDs to inhibit the activity of MAIT cells.

Methods

Circulating CD161+ and IL-18Rα+ TCRVα7.2+ MAIT cells from pSS patients and healthy controls (HC) were assessed using flow cytometry, and expression of CCR9, CXCR5, and IL-7R on MAIT cells was studied. Production of IFN-γ and IL-21 by MAIT cells was measured upon IL-7 stimulation in the presence of leflunomide (LEF) and hydroxychloroquine (HCQ).

Results

The numbers of CD161+ and IL-18Rα+ MAIT cells were decreased in pSS patients compared to HC. Relative increased percentages of CD4 MAIT cells in pSS patients caused significantly higher CD4/CD8 ratios in MAIT cells. The numbers of CCR9 and CXCR5-expressing MAIT cells were significantly higher in pSS patients. IL-7R expression was higher in CD8 MAIT cells as compared to all CD8 T cells, and changes in IL-7R expression correlated to several clinical parameters. The elevated production of IL-21 by MAIT cells was significantly inhibited by LEF/HCQ treatment.

Conclusion

Circulating CD161+ and IL-18Rα+ MAIT cell numbers are decreased in pSS patients. Given their enriched CCR9/CXCR5 expression this may facilitate migration to inflamed salivary glands known to overexpress CCL25/CXCL13. Given the pivotal role of IL-7 and IL-21 in inflammation in pSS this indicates a potential role for MAIT cells in driving pSS immunopathology.

Regulation of immune cell metabolism in health and disease: Special focus on T and B cell subsets

Metabolism is a dynamic process and keeps changing from time to time according to the demand of a particular cell to meet its bio-energetic requirement. Different immune cells rely on distinct metabolic programs which allow the cell to balance its requirements for energy, molecular biosynthesis, and effector activity. In the aspect of infection and cancer immunology, effector T and B cells get exhausted and help tumor cells to evade immunosurveillance. On the other hand, T cells become hyperresponsive in the scenario of autoimmune diseases. In this article, we have explored the uniqueness and distinct metabolic features of key CD4⁺ T and B helper cell subsets, CD4⁺ T, B regulatory cell subsets and CD8⁺ T cells regarding health and disease. Th1 cells rely on glycolysis and glutaminolysis; inhibition of these metabolic pathways promotes Th1 cells in Treg population. However, Th2 cells are also dependent on glycolysis but an abundance of lactate within TME shifts their metabolic dependency to fatty acid metabolism. Th17 cells depend on HIF-1α mediated glycolysis, ablation of HIF-1α reduces Th17 cells but enhance Treg population. In contrast to effector T cells which are largely dependent on glycolysis for their differentiation and function, Treg cells mainly rely on FAO for their function. Therefore, it is of utmost importance to understand the metabolic fates of immune cells and how it facilitates their differentiation and function for different disease models. Targeting metabolic pathways to restore the functionality of immune cells in diseased conditions can lead to potent therapeutic measures.

Elevated CXCL13 in primary Sjögren's syndrome and its correlation with disease activity: a systematic review and meta-analysis

OBJECTIVES

CXCL13 levels have been reported to be elevated in primary Sjögren's syndrome (pSS) patients. This study investigated alterations involving the CXCL13/CXCR5 axis in pSS patients and explored the correlation between CXCL13 expression and disease severity.

METHODS

Six databases, including PubMed, Web of Science, Embase, Ovid Medline, China National Knowledge Infrastructure, and Wanfang, were searched. The quality of the included studies was assessed using the Newcastle-Ottawa Scale criteria. We analyzed CXCL13 concentrations in the serum and saliva of pSS patients and healthy controls (HCs). Next, we analyzed the percentage of CXCR5⁺CD4⁺ T cells among CD4⁺ T cells in pSS patients and HCs. Correlations between CXCL13 levels and serological, clinical, and histological parameters of patients were also assessed. Publication bias was determined using funnel plots and Egger's test.

RESULTS

Twenty-three articles were included; of these, 14 studies reported CXCL13 levels, and 5 reported CXCR5⁺CD4⁺ T cell count of pSS patients and HCs. Nine articles covering 32 studies reported correlations between serum CXCL13 levels and serological, clinical, and histological parameters in pSS patients. Expressions of CXCL13 and CXCR5⁺CD4⁺ T cell count were significantly increased in pSS patients compared with those in HCs. There was a positive correlation between CXCL13 levels and serum IgG levels, disease activity indices, and focus score in minor salivary gland biopsy of patients.

CONCLUSIONS

CXCL13 abundance was evidently elevated in pSS patients and correlated with disease activity and can therefore probably be employed as a robust biomarker to monitor and diagnose pSS. Key Points • Serum CXCL13 is significantly elevated in primary Sjögren's syndrome patients. • CXCL13 level correlates with disease severity and activity of primary Sjögren's syndrome. • CXCL13 can probably be used as a robust biomarker to monitor and diagnose primary Sjögren's syndrome.

Role of the CXCL13/CXCR5 Axis in Autoimmune Diseases

CXCL13 is a B-cell chemokine produced mainly by mesenchymal lymphoid tissue organizer cells, follicular dendritic cells, and human T follicular helper cells. By binding to its receptor, CXCR5, CXCL13 plays an important role in lymphoid neogenesis, lymphoid organization, and immune responses. Recent studies have found that CXCL13 and its receptor CXCR5 are implicated in the pathogenesis of several autoimmune diseases, such as rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, primary Sjögren’s syndrome, myasthenia gravis, and inflammatory bowel disease. In this review, we discuss the biological features of CXCL13 and CXCR5 and the recent findings on the pathogenic roles of the CXCL13/CXCR5 axis in autoimmune diseases. Furthermore, we discuss the potential role of CXCL13 as a disease biomarker and therapeutic target in autoimmune diseases.

Characterization of comprehensive dynamic epigenetic changes during human primary Sjögren's syndrome progression

Background

Primary Sjögren’s syndrome (pSS) is a systemic autoimmune disease characterized by reduced exocrine gland (principally the salivary and lacrimal glands) activity caused by chronic lymphocytic infiltration. Although pSS has been closely associated with an increased risk of mucosa-associated lymphoid tissue (MALT) lymphoma, the dynamic epigenetic changes in the gland cells that accompany the pathogenesis are not entirely understood.

Methods

In this study, we harvested tissue samples from the labial gland with (LG_pSS) or without pSS (LG_NC) before MALT development, as well as the parotid gland with tumor tissues (PG_MALT) and paracancerous tissues (PG_NC) of two pSS patients with MALT lymphoma, and conducted RNA-seq and ChIP-seq for tri-methylated histone 3 lysine 4, 9, 27, 36, and 79 (H3K4/9/27/36/79me3).

Results

Transcriptome landscapes indicated two outcomes of pSS progression with or without MALT lymphoma represented by distinct populations of differentially expressed genes and their functions. Furthermore, the epigenetic atlas of genome-wide H3K4/9/27/36/79me3 was in different stages for various samples, indicating that the variance of H3K4me3 was the earliest event, followed by selective alterations of H3K9/27/36/79me3. These four epigenetic modifications determine the final outcome of pSS progression.

Conclusions

Our results not only advance the understanding of the dynamics of pSS progression and highlight the importance of epigenetic alterations in regulating transcription during this pathological process, but also identify potential therapeutic targets for pSS treatment and lymphoma intervention.

CP-25 alleviates antigen-induced experimental Sjögren's syndrome in mice by inhibiting JAK1-STAT1/2-CXCL13 signaling and interfering with B-cell migration

The etiology of primary Sjögren's syndrome (pSS) remains unknown, and there is no complete curative drug. In this study, we treated a mouse model of the submandibular gland (SG) protein-immunized experimental Sjögren's syndrome (ESS) with paeoniflorin-6'-O-benzene sulfonate (termed CP-25) to evaluate the potential therapeutic effects of CP-25. Through in vivo experiments, we found that CP-25 increased saliva flow, alleviated the salivary gland indexes, and improved tissue integrity in the ESS model. The viability of splenocytes and B-lymphocyte migration from spleen were reduced in ESS mice. Furthermore, CP-25 decreased the expression of IgG antibodies, anti-SSA and anti-SSB antibodies and modulated the levels of cytokines in the serum of SS mice. The numbers of total B lymphocytes, plasma cells (PCs), and memory B cells diminished in the salivary gland. Increased expression of the JAK1-STAT1-CXCL13 axis and IFNα was found in human tissue isolated from pSS patients. In vitro, after stimulation with IFNα, the levels of CXCL13 mRNA and CXCL13 in human salivary gland epithelial cells (HSGEC) increased, while CP-25 counteracted the secretion of CXCL13 and downregulated the expression of CXCL13. IFN-α activated the JAK1-STAT1/2-CXCL13 signaling pathway in HSGEC, which was negatively regulated by additional CP-25. As a consequence, B-cell migration was downregulated in coculture with IFN-α-stimulated HSGEC. Taken together, this study demonstrated that the therapeutic effects of CP-25 were associated with the inhibition of the JAK1-STAT1/2-CXCL13 signaling pathway in HSGEC, which impedes the migration of B cells into the salivary gland. We identified the underlying mechanisms of the therapeutic effect of CP-25 and provided an experimental foundation for CP-25 as a potential drug in the treatment of the human autoimmune disorder pSS.

Transcriptome Analysis of CCR9+ T Helper Cells From Primary Sjögren's Syndrome Patients Identifies CCL5 as a Novel Effector Molecule

Introduction

CCR9+ Tfh-like pathogenic T helper (Th) cells are elevated in patients with primary Sjögren’s syndrome (pSS) and indicated to play a role in pSS immunopathology. Here we delineate the CCR9+ Th cell-specific transcriptome to study the molecular dysregulation of these cells in pSS patients.

Methods

CCR9+, CXCR5+ and CCR9-CXCR5- Th cells from blood of 7 healthy controls (HC) and 7 pSS patients were FACS sorted and RNA sequencing was performed. Computational analysis was used to identify differentially expressed genes (DEGs), coherent gene expression networks and differentially regulated pathways. Target genes were replicated in additional cohorts.

Results

5131 genes were differentially expressed between CCR9+ and CXCR5+ Th cells; 6493 and 4783 between CCR9+ and CCR9-CXCR5- and between CXCR5+ and CCR9-CXCR5-, respectively. In the CCR9+ Th cell subset 2777 DEGs were identified between HC and pSS patients, 1416 and 1077 in the CXCR5+ and CCR9-CXCR5- subsets, respectively. One gene network was selected based on eigengene expression differences between the Th cell subsets and pathways enriched for genes involved in migration and adhesion, cytokine and chemokine production. Selected DEGs of interest (HOPX, SOX4, ITGAE, ITGA1, NCR3, ABCB1, C3AR1, NT5E, CCR5 and CCL5) from this module were validated and found upregulated in blood CCR9+ Th cells, but were similarly expressed in HC and pSS patients. Increased frequencies of CCR9+ Th cells were shown to express higher levels of CCL5 than CXCR5+ and CCR9-CXCR5- Th cells, with the highest expression confined to effector CCR9+ Th cells. Antigenic triggering and stimulation with IL-7 of the Th cell subsets co-cultured with monocytes strongly induced CCL5 secretion in CCR9+ Th cell cocultures. Additionally, effector CCR9+ Th cells rapidly released CCL5 and secreted the highest CCL5 levels upon stimulation.

Conclusion

Transcriptomic analysis of circulating CCR9+ Th cells reveals CCR9-specific pathways involved in effector T cell function equally expressed in pSS patients and HC. Given the increased numbers of CCR9+ Th cells in the blood and inflamed glands of pSS patients and presence of inflammatory stimuli to activate these cells this suggests that CCR9-specific functions, such as cell recruitment upon CCL5 secretion, could significantly contribute to immunopathology in pSS.

Characterization of Extracellular Vesicle Cargo in Sjögren's Syndrome through a SWATH-MS Proteomics Approach

Primary Sjögren’s syndrome (pSS) is a complex heterogeneous disease characterized by a wide spectrum of glandular and extra-glandular manifestations. In this pilot study, a SWATH-MS approach was used to monitor extracellular vesicles-enriched saliva (EVs) sub-proteome in pSS patients, to compare it with whole saliva (WS) proteome, and assess differential expressed proteins between pSS and healthy control EVs samples. Comparison between EVs and WS led to the characterization of compartment-specific proteins with a moderate degree of overlap. A total of 290 proteins were identified and quantified in EVs from healthy and pSS patients. Among those, 121 proteins were found to be differentially expressed in pSS, 82% were found to be upregulated, and 18% downregulated in pSS samples. The most representative functional pathways associated to the protein networks were related to immune-innate response, including several members of S100 protein family, annexin A2, resistin, serpin peptidase inhibitors, azurocidin, and CD14 monocyte differentiation antigen. Our results highlight the usefulness of EVs for the discovery of novel salivary-omic biomarkers and open novel perspectives in pSS for the identification of proteins of clinical relevance that could be used not only for the disease diagnosis but also to improve patients’ stratification and treatment-monitoring. Data are available via ProteomeXchange with identifier PXD025649.

Salivary concentrations of cytokines and other analytes in healthy children

BACKGROUND

Blood has been the usual biological fluid for measuring analytes, but there is mounting evidence that saliva may be also useful for detecting cytokines in a noninvasive way. Thus, in this study we aimed to determine concentration of cytokines and other analytes in saliva from a population of healthy children.

METHODS

We collected un-stimulated whole saliva samples from clinically healthy children, and concentration of 17 cytokines and 12 other analytes were measured in supernatants. All values were adjusted by albumin content and were log-transformed before multivariate statistical analysis.

RESULTS

We included 114 children (53.5% females) between 6.0 and 11.9 years old. The highest concentrations (medians, pg/µg albumin) were seen for visfatin (183.70) and adiponectin (162.26) and the lowest for IL-13 and IL-2 (~0.003). Albumin concentration was associated with age (r_S = 0.39, p < 0.001). In the multivariate analysis, five analytes (C peptide, ghrelin, GLP-1, glucagon, leptin) inversely correlated with age and positively with height-for-age. Age was also positively associated with PAI-1, while height-for-age was also positively associated with insulin and visfatin. Finally, BMI-for-age had a positive correlation with GM-CSF and insulin.

CONCLUSIONS

Herein, we provided concentration values for 29 analytes in saliva from healthy children that may be useful as preliminary reference framework in the clinical research setting.

Decreased circulating CXCR3 + CCR9+T helper cells are associated with elevated levels of their ligands CXCL10 and CCL25 in the salivary gland of patients with Sjögren's syndrome to facilitate their concerted migration

CCR9 + T helper (Th) cells can induce Sjögren-like symptoms in mice and both CCR9 + Th cells and their ligand CCL25 are increased in the salivary glands of primary Sjögren's syndrome (pSS) patients. Increased circulating CCR9 + Th cells are present in pSS patients. CCR9 + Th cells are hyperresponsive to IL-7, secrete high levels of IFN-γ, IL-21, IL-17 and IL-4 and potently stimulate B cells in both patients and healthy individuals. Our aim was to study co-expression of chemokine receptors on CCR9 + Th cells and whether in pSS this might differentially affect CCR9 + Th cell frequencies. Frequencies of circulating CCR9 + and CCR9- Th cells co-expressing CXCR3, CCR4, CCR6 and CCR10 were studied in pSS patients and healthy controls. CCL25, CXCL10, CCL17, CCL20 and CCL27 mRNA and protein expression of salivary gland tissue of pSS and non-Sjögren's sicca (non-SS) patients was assessed. Chemotaxis assays were performed to study migration induced by CXCL10 and CCL25. Higher expression of CXCR3, CCR4 and CCR6 but not CCR10 was observed on CCR9 + Th cells as compared to cells lacking CCR9. Decreased frequencies of circulating memory CCR9 + CXCR3+ Th cells were found in pSS patients, which was most pronounced in the effector memory subset. Increased salivary gland CCL25 and CXCL10 expression significantly correlated and both ligands functioned synergistically based on in vitro induced chemotaxis. Decreased memory CXCR3 + CCR9+ Th cells in blood of pSS patients may be due to a concerted action of overexpressed ligands at the site of inflammation in the salivary glands facilitating their preferential migration and positioning in the lymphocytic infiltrates.

Emerging roles for chemokines and cytokines as orchestrators of immunopathology in Sjögren's syndrome

In primary SS (pSS), chemokines and cytokines orchestrate immunopathology driven by a complex network of interacting inflammatory cells. In recent years, the importance of chemotactic and non-chemotactic cytokines that control function, movement and placing of all cells within the inflamed exocrine glands and directing immunopathology has become increasingly clear. This paper reviews the current knowledge on chemokines and focuses on the emerging roles of novel chemotactic and non-chemotactic mediators in pSS. It highlights their contribution to pathogenic processes such as B cell hyperactivity and the formation of ectopic lymphoid structures. To this end, the role of acquired (CXCR5/CCR9 Th-cell-mediated) and innate (inflammasome/IL-1/IL-18-mediated) pathways in steering immunopathology is discussed.