The role of ectopic germinal centers in the immunopathology of primary Sjögren's syndrome: a systematic review

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.

More severe parotid gland histopathology in paediatric-onset than in adult-onset Sjögren's disease

OBJECTIVES

The aim of this study was to assess the histopathological features of the parotid glands in patients with paediatric-onset Sjögren's disease (pedSjD) in comparison to patients with adult-onset Sjögren's disease (adSjD).

METHODS

This study was performed in Groningen, the Netherlands. Patients with pedSjD from a diagnostic paediatric cohort (n=19), patients with adSjD from a diagnostic adult cohort (n=32) and patients with adSjD who participated in a clinical trial (n=42) with a baseline parotid gland biopsy were included. Parotid gland biopsies were analysed after (immuno)histological staining for SjD-related histopathological markers and compared between groups.

RESULTS

All characteristic histopathological features of adSjD were also observed in pedSjD. There were no significant differences in lymphoepithelial lesions or immunoglobulin A (IgA)/IgG plasma cell shift between the pedSjD and the adSjD cohorts. However, compared with the diagnostic adSjD cohort (with comparable total EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) scores), pedSjD showed more severe lymphocytic infiltration as reflected by a higher focus score (p=0.003), a higher relative surface area of CD45+ infiltrate (p=0.041), higher numbers of B and T lymphocytes/mm2 (p=0.004 and p=0.029, respectively), a higher B/T lymphocyte ratio (p=0.013), higher numbers of CD21+ follicular dendritic cell networks/mm2 (p=0.029) and germinal centres (GC)/mm2 (p=0.002). Compared with the trial adSjD cohort, with significant higher total ESSDAI scores (p=0.001), only the B/T lymphocyte ratio and numbers of GC/mm2 were significantly higher in the pedSjD cohort (p=0.023 and p=0.018, respectively).

CONCLUSION

Patients with pedSjD exhibit more pronounced histopathological features compared with patients with adSjD at diagnosis. Notably, the histopathology of patients with pedSjD aligns more closely with that observed in an adSjD clinical trial cohort, with even stronger B lymphocyte involvement.

Connecting salivary gland inflammation to specific symptoms in Sjögren's disease

INTRODUCTION

The complex nature of Sjögren's Disease (SjD) necessitates a comprehensive and patient-centered approach in both diagnosis and management. This narrative review emphasizes the need for a holistic understanding of the connection between salivary gland inflammation and oral symptoms in SjD.

AREAS COVERED

The intricate relationship between salivary gland inflammation and dry mouth is explored, highlighting the variability in associations reported in studies. The association of the severity of xerostomia and degree of inflammation is also discussed. The frequent presence of recurrent sialadenitis in SjD further accentuates the connection of compromised salivary gland function and inflammation. The review additionally discusses local inflammatory factors assessed through salivary gland biopsies, which could potentially serve as predictors for lymphoma development in SjD. Insights into compromised quality of life and hypercoagulable state and their association with salivary gland inflammations are provided. Advancements in noninvasive imaging techniques, particularly salivary gland ultrasonography and color Doppler ultrasound, offer promising avenues for noninvasive assessment of inflammation.

EXPERT OPINION

There is a need for longitudinal studies to unravel the connections between salivary gland inflammation and oral symptoms. This will enhance management strategies and optimize treatment outcomes for SjD patients.

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.

Exploring Salivary Epithelial Dysfunction in Sjögren's Disease

Sjögren's Disease (SjD) is an autoimmune disease of the exocrine tissues. Etiological events result in the loss of epithelial homeostasis alongside extracellular matrix (ECM) destruction within the salivary and lacrimal glands, followed by immune cell infiltration. In this review, we have assessed the current understanding of epithelial-mesenchymal transition (EMT)-associated changes within the salivary epithelium potentially involved in salivary dysfunction and SjD pathogenesis. We performed a PubMed literature review pertaining to the determination of pathogenic events that lead to EMT-related epithelial dysfunction and signaling in SjD. Molecular patterns of epithelial dysfunction in SjD salivary glands share commonalities with EMT mediating wound healing. Pathological changes altering salivary gland integrity and function may precede direct immune involvement while perpetuating MMP9-mediated ECM destruction, inflammatory mediator expression, and eventual immune cell infiltration. Dysregulation of EMT-associated factors is present in the salivary epithelium of SjD and may be significant in initiating and perpetuating the disease. In this review, we further highlight the gap regarding mechanisms that drive epithelial dysfunction in salivary glands in the early or subclinical pre-lymphocytic infiltration stages of SjD.

Molecular B-cell clonality assay in minor salivary glands as a useful tool for the lymphoma risk assessment in Sjögren's syndrome

OBJECTIVES

Non-Hodgkin's lymphoma (NHL) risk assessment is crucial in Sjögren's syndrome (SS). We studied the prevalence of clonal immunoglobulin gene rearrangements in minor salivary glands (MSG) and their correlations with lymphoma occurrence and with previously established NHL predictors.

METHODS

Molecular B-cell expansion was studied in fresh-frozen MSG of 207 patients with either suspected SS or with suspected lymphoma during SS, using a standardised multiplex PCR assay combined with heteroduplex analysis by microcapillary electrophoresis. The assignation of clonal cases was based on EuroClonality consortium guidelines.

RESULTS

Among 207 studied patients, 31 (15%) had MSG monoclonal B-cell infiltration. Monoclonality was significantly more frequent in patients with SS (28/123, 22.8%) compared with patients without SS (3/84, 3.6%, P<0.001). Monoclonal B-cell infiltration in MSG of SS patients correlated significantly with ongoing salivary gland NHL, salivary gland swelling, CD4+ T-cell lymphopenia, rheumatoid factor (RF) activity, low complement levels and type 2 mixed cryoglobulinemia. The accumulation of biological risk factors was associated with a higher rate of MSG B-cell monoclonality given that patients with only positive RF had no probability of MSG B-cell monoclonality, RF-positive patients with 1 or 2 other risk factors had a 25.0% and 85.7% probability of MSG B-cell monoclonality, respectively.

CONCLUSION

The detection of MSG monoclonal B-cell expansion by this easy-to-perform molecular assay is useful, both at the time of diagnosis and during the course of SS. Monoclonal B-cell expansion is associated with a subset of SS patients presenting either ongoing lymphoma or other established lymphoma predictive factors.

Prognostic significance of lymphocytic foci composition in minor salivary gland biopsies for severe disease flare and severity in Sjögren's syndrome: a 3-year follow-up cohort study

Introduction

This was an ambispective cohort study evaluating the prognostic significance of lymphocytic foci and its lymphoid composition in minor salivary gland biopsy (MSGB) for short-term disease flare and severity in Sjögren's syndrome (SS).

Methods

The inclusion criteria comprised individuals meeting the ACR/EULAR 2016 criteria who underwent MSGB with an infiltration of more than 50 lymphocytes and received clinical diagnosis between September 2017 and December 2018. Patients with inadequate biopsy samples were excluded. The number of lymphocytic foci and their lymphoid composition in MSGB were assessed using immunofluorescence staining. Major organ damage and improvements in the EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) were measured. Statistical analyses, including Cox and linear regressions, were conducted.

Results

A total of 78 patients with at least one lymphocytic focus were included in the study. The presence of higher T-cell counts in lymphocytic foci in MSGB was associated with severe disease flare, and a logarithmic transformation of T-cell count indicated increased risk (HR 1.96, 95% CI 0.91-4.21). Improvements in the ESSDAI were associated with higher total lymphocyte count and T- and B-cell numbers in the lymphoid composition of the lymphocytic foci. Seropositive patients exhibited higher T CD4+ cell numbers. Correlation analysis showed negative associations between age and lymphocytic foci and the T-cell count. Positive correlations were observed between antinuclear antibody (ANA) titers and total lymphocyte numbers.

Discussion

Patients with a higher number of T cells in the lymphocytic infiltrates of lymphocytic foci may have a two-fold risk of severe disease flare. The number of B cells and T CD4+ cells in the lymphocytic infiltrates of lymphocytic foci showed a weak but positive relation with the ESSDAI improvement during follow-up. Age and seropositivity appeared to influence the lymphoid composition of the lymphocytic foci.

Tertiary lymphoid structures in autoimmune diseases

Tertiary lymphoid structures (TLSs) are organized lymphoid-like aggregations in non-lymphoid tissues. Tissues with chronic and persistent inflammation infiltration may drive and form ectopic germinal center-like structures, which are very common in autoimmune diseases, chronic infections, and tumor microenvironments. However, the mechanisms governing the formation of TLSs are still being explored. At present, it is not clear whether the formation of TLSs is associated with local uncontrolled immune inflammatory responses. While TLSs suggest a good prognosis in tumors, the opposite is true in autoimmune diseases. This review article will discuss the current views on initiating and maintaining TLSs and the potential therapeutic target in autoimmune diseases.

Is minor salivary gland biopsy still mandatory in Sjogren's syndrome? Does seronegative Sjogren's syndrome exist?

Sjӧgren's disease (SjD) is a systemic autoimmune disorder characterized by the chronic inflammation and dysfunction of exocrine glands, mainly salivary glands, causing dryness of the eyes and of the mouth. The disease may affect different organs and tissues with complex and heterogeneous clinical presentation, usually with sicca symptoms, profound fatigue, chronic pain, major organ involvement, and lymphomas. SjD diagnosis is based on the combination of clinical, serological, and functional tests with histological biomarkers. Minor salivary gland biopsy (mSGB) represents the cornerstone for the diagnosis of SjD, allowing the study of the characteristic focal infiltration of B- and T lymphocytes. Besides, mSGB might also have a prognostic role, being the infiltrates more complex in patients with severe SjD. But biopsy, so far, is not mandatory for SjD and mSG ultrasound and peripheral biomarkers might replace its role in the future. Another important aspect of SjD is the presence of autoantibodies, although 20 to 30% of patients are "seronegative" for specific autoantibodies (ANA, antiRo/SSA, antiLa/SSB). The characteristics of this subset of patients are currently under evaluation and "new" autoantibodies and biomarkers might be necessary for better patient's stratification and follow-up.

A bibliometric analysis of primary Sjögren's syndrome-associated lymphoma from 1991 to 2022

Background

Patients with primary Sjögren's syndrome (pSS) take a higher risk of developing lymphoma, which is the most frequent cause of death in pSS. Based on this situation, the number of publications focusing on pSS-associated lymphoma has been growing. Nevertheless, the extent, range, and nature of available research in this field have not been systematically summarized. This study aimed to map the literature available on pSS-associated lymphoma and identify global hotspots and trends.

Methods

Papers on pSS and lymphoma published from 1991 to 2022 were searched from the Web of Science Core Collection. Microsoft Excel, SPSS Statistics, VOSviewer, and CiteSpace software were used to analyze and visualize the quantity and citations of publications, and the global research hotspots and trends of pSS-associated lymphoma.

Results

629 publications from 50 countries/regions and 538 institutions were included in this study. From 1991 to 2022, the cumulative publications steadily increased. The USA ranked first in the number of publications (n = 118, 18.76 %), followed by Italy (n = 94, 14.94 %) and France (n = 73, 11.61 %). Udine University (n = 29) and Salvatore De Vita (n = 39) were the most prolific affiliation and author, respectively. Claudio Vitali was the most frequently cited author (n = 335). In total, the most frequently occurring keywords were clustered into four well-defined groups. The first group of keywords pointed to the clinical assessment and treatment of pSS-associated lymphoma. The second group highlighted the pathogenesis. The third group identified the predictors and prognosis of pSS-associated Lymphoma, while the fourth group focused on interstitial lung disease and pulmonary lymphoma in patients with pSS. Currently, the hot keywords include consensus, disease activity, and pathogenesis. Ultrasonography, mucosa-associated lymphoid tissue (MALT) lymphoma, and epidemiology are the emerging research trends in pSS-associated lymphoma.

Conclusion

Research on pSS-associated lymphoma is burgeoning. Despite clinical assessment, treatment and pathogenesis, researchers also showed great interest in the predictors, prognosis, and pulmonary manifestations of pSS-associated lymphoma. Current research of pSS-associated lymphoma mainly focuses on consensus, disease activity, and pathogenesis, while the emerging research trends in pSS are pointing to ultrasonography, MALT lymphoma and epidemiology.

Normal and Sjogren's syndrome models of the murine lacrimal gland studied at single-cell resolution

The lacrimal gland is of central interest in ophthalmology both as the source of the aqueous component of tear fluid and as the site of autoimmune pathology in the context of Sjogren's syndrome (SjS). To provide a foundational description of mouse lacrimal gland cell types and their patterns of gene expression, we have analyzed single-cell transcriptomes from wild-type (Balb/c) mice and from two genetically based SjS models, MRL/lpr and NOD (nonobese diabetic).H2b, and defined the localization of multiple cell-type-specific protein and mRNA markers. This analysis has uncovered a previously undescribed cell type, Car6+ cells, which are located at the junction of the acini and the connecting ducts. More than a dozen secreted polypeptides that are likely to be components of tear fluid are expressed by acinar cells and show pronounced sex differences in expression. Additional examples of gene expression heterogeneity within a single cell type were identified, including a gradient of Claudin4 along the length of the ductal system and cell-to-cell heterogeneity in transcription factor expression within acinar and myoepithelial cells. The patterns of expression of channels, transporters, and pumps in acinar, Car6+, and ductal cells make strong predictions regarding the mechanisms of water and electrolyte secretion. In MRL/lpr and NOD.H2b lacrimal glands, distinctive changes in parenchymal gene expression and in immune cell subsets reveal widespread interferon responses, a T cell-dominated infiltrate in the MRL/lpr model, and a mixed B cell and T cell infiltrate in the NOD.H2b model.

Targeting plasma cells in systemic autoimmune rheumatic diseases - Promises and pitfalls

Plasma cells are the antibody secretors of the immune system. Continuous antibody secretion over years can provide long-term immune protection but could also be held responsible for long-lasting autoimmunity in case of self-reactive plasma cells. Systemic autoimmune rheumatic diseases (ARD) affect multiple organ systems and are associated with a plethora of different autoantibodies. Two prototypic systemic ARDs are systemic lupus erythematosus (SLE) and Sjögren's disease (SjD). Both diseases are characterized by B-cell hyperactivity and the production of autoantibodies against nuclear antigens. Analogues to other immune cells, different subsets of plasma cells have been described. Plasma cell subsets are often defined dependent on their current state of maturation, that also depend on the precursor B-cell subset from which they derived. But, a universal definition of plasma cell subsets is not available so far. Furthermore, the ability for long-term survival and effector functions may differ, potentially in a disease-specific manner. Characterization of plasma cell subsets and their specificity in individual patients can help to choose a suitable targeting approach for either a broad or more selective plasma cell depletion. Targeting plasma cells in systemic ARDs is currently challenging because of side effects or varying depletion efficacies in the tissue. Recent developments, however, like antigen-specific targeting and CAR-T-cell therapy might open up major benefits for patients beyond current treatment options.

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.

Outline of Salivary Gland Pathogenesis of Sjögren's Syndrome and Current Therapeutic Approaches

Sjögren's syndrome (SS) is an autoimmune disease characterized by the involvement of exocrine glands such as the salivary and lacrimal glands. The minor salivary glands, from which tissue samples may be obtained, are important for the diagnosis, evaluation of therapeutic efficacy, and genetic analyses of SS. In the onset of SS, autoantigens derived from the salivary glands are recognized by antigen-presenting dendritic cells, leading to the activation of T and B cells, cytokine production, autoantibody production by plasma cells, the formation of ectopic germinal centers, and the destruction of salivary gland epithelial cells. A recent therapeutic approach with immune checkpoint inhibitors for malignant tumors enhances the anti-tumor activity of cytotoxic effector T cells, but also induces SS-like autoimmune disease as an adverse event. In the treatment of xerostomia, muscarinic agonists and salivary gland duct cleansing procedure, as well as sialendoscopy, are expected to ameliorate symptoms. Clinical trials on biological therapy to attenuate the hyperresponsiveness of B cells in SS patients with systemic organ involvement have progressed. The efficacy of treatment with mesenchymal stem cells and chimeric antigen receptor T cells for SS has also been investigated. In this review, we will provide an overview of the pathogenesis of salivary gland lesions and recent trends in therapeutic approaches for SS.

The Role of Regulatory T Cells in the Onset and Progression of Primary Sjögren's Syndrome

Regulatory T cells (Tregs) play a key role in maintaining immune balance and regulating the loss of self-tolerance mechanisms in various autoimmune diseases, including primary Sjögren's syndrome (pSS). With the development of pSS primarily in the exocrine glands, lymphocytic infiltration occurs in the early stages, mainly due to activated CD4⁺ T cells. Subsequently, in the absence of rational therapy, patients develop ectopic lymphoid structures and lymphomas. While the suppression of autoactivated CD4⁺ T cells is involved in the pathological process, the main role belongs to Tregs, making them a target for research and possible regenerative therapy. However, the available information about their role in the onset and progression of this disease seems unsystematized and, in certain aspects, controversial. In our review, we aimed to organize the data on the role of Tregs in the pathogenesis of pSS, as well as to discuss possible strategies of cell therapy for this disease. This review provides information on the differentiation, activation, and suppressive functions of Tregs and the role of the FoxP3 protein in these processes. It also highlights data on various subpopulations of Tregs in pSS, their proportion in the peripheral blood and minor salivary glands of patients as well as their role in the development of ectopic lymphoid structures. Our data emphasize the need for further research on Tregs and highlight their potential use as a cell-based therapy.

Ectopic lymphoid structures in the aged lacrimal glands

Aging is a complex biological process in which many organs are pathologically affected. We previously reported that aged C57BL/6J had increased lacrimal gland (LG) lymphoid infiltrates that suggest ectopic lymphoid structures. However, these ectopic lymphoid structures have not been fully investigated. Using C57BL/6J mice of different ages, we analyzed the transcriptome of aged murine LGs and characterized the B and T cell populations. Age-related changes in the LG include increased differentially expressed genes associated with B and T cell activation, germinal center formation, and infiltration by marginal zone-like B cells. We also identified an age-related increase in B1+ cells and CD19+B220+ cells. B220+CD19+ cells were GL7+ (germinal center-like) and marginal zone-like and progressively increased with age. There was an upregulation of transcripts related to T follicular helper cells, and the number of these cells also increased as mice aged. Compared to a mouse model of Sjögren syndrome, aged LGs have similar transcriptome responses but also unique ones. And lastly, the ectopic lymphoid structures in aged LGs are not exclusive to a specific mouse background as aged diverse outbred mice also have immune infiltration. Altogether, this study identifies a profound change in the immune landscape of aged LGs where B cells become predominant. Further studies are necessary to investigate the specific function of these B cells during the aged LGs.

Extranodal marginal zone lymphoma clonotypes are detectable prior to eMZL diagnosis in tissue biopsies and peripheral blood of Sjögren's syndrome patients through immunogenetics

Introduction

Activated B cells play a key role in the pathogenesis of primary Sjögren's syndrome (pSS) through the production of autoantibodies and the development of ectopic germinal centers in the salivary glands and other affected sites. Around 5-10% of pSS patients develop B-cell lymphoma, usually extranodal marginal zone lymphomas (eMZL) of the mucosa-associated lymphoid tissue (MALT). The aim of the current study is to investigate if the eMZL clonotype is detectable in prediagnostic blood and tissue biopsies of pSS patients.

Methods/Results

We studied prediagnostic tissue biopsies of three pSS patients diagnosed with eMZL and four pSS controls through immunoglobulin (IG) gene repertoire sequencing. In all three cases, we observed the eMZL clonotype in prediagnostic tissue biopsies. Among controls, we observed transient elevation of clonotypes in two pSS patients. To evaluate if eMZL clonotypes may also be detected in the circulation, we sequenced a peripheral blood mononuclear cell (PBMC) sample drawn at eMZL diagnosis and two years prior to eMZL relapse in two pSS patients. The eMZL clonotype was detected in the peripheral blood prior to diagnosis in both cases. Next, we selected three pSS patients who developed eMZL lymphoma and five additional pSS patients who remained lymphoma-free. We sequenced the IG heavy chain (IGH) gene repertoire in PBMC samples taken a median of three years before eMZL diagnosis. In two out of three eMZL patients, the dominant clonotype in the prediagnostic PBMC samples matched the eMZL clonotype in the diagnostic biopsy. The eMZL clonotypes observed consisted of stereotypic IGHV gene combinations (IGHV1-69/IGHJ4 and IGHV4-59/IGHJ5) associated with rheumatoid factor activity, a previously reported feature of eMZL in pSS.

Discussion

In conclusion, our results indicate that eMZL clonotypes in pSS patients are detectable prior to overt eMZL diagnosis in both tissue biopsies and peripheral blood through immunogenetic sequencing, paving the way for the development of improved methods of early detection of eMZL.

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.

Predisposing Factors, Clinical Picture, and Outcome of B-Cell Non-Hodgkin’s Lymphoma in Sjögren’s Syndrome

Among other systemic autoimmune diseases, primary Sjögren syndrome (pSS) bears the highest risk for lymphoma development. In pSS, chronic antigenic stimulation gradually drives the evolution from polyclonal B-cell expansion to oligoclonal/monoclonal B-cell predominance to malignant B-cell transformation. Thus, most pSS-related lymphomas are B-cell non-Hodgkin lymphomas (NHLs), with mucosa-associated lymphoid tissue (MALT) lymphomas predominating, followed by diffuse large B-cell lymphomas (DLBCLs) and nodal marginal zone lymphomas (NMZLs). Since lymphomagenesis is one of the most serious complications of pSS, affecting patients’ survival, a plethora of possible predisposing factors has been studied over the years, ranging from classical clinical, serological, hematological, and histological, to the more recently proposed genetic and molecular, allowing clinicians to timely detect and to closely follow-up the subgroup of pSS patients with increased risk for lymphoma development. Overall predisposing factors for pSS-related lymphomagenesis reflect the status of B-cell hyperactivity. Different clinical features have been described for each of the distinct pSS-related B-cell NHL subtypes. While generally pSS patients developing B-cell NHLs display a fairly good prognosis, outcomes in terms of treatment response and survival rates seem to differ depending on the lymphoma subtype, with MALT lymphomas being characterized by a rather indolent course and DLBCLs gravely affecting patients’ survival.

Not all autoantibodies are clinically relevant. Classic and novel autoantibodies in Sjögren’s syndrome: A critical review

Sjögren’s syndrome (SjS) is a heterogeneous systemic disease. The abnormal responses to La/SSB and Ro/SSA of both B-cells and T-cells are implicated as well as others, in the destruction of the epithelium of the exocrine glands, whose tissue characteristically shows a peri-epithelial lymphocytic infiltration that can vary from sicca syndrome to systemic disease and lymphoma. Despite the appearance of new autoantibodies, anti-Ro/SSA is still the only autoantibody included in the American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) classification criteria and is used extensively as a traditional biomarker in clinical practice. The study and findings of new autoantibodies in SjS has risen in the previous decade, with a central role given to diagnosis and elucidating new aspects of SjS physiopathology, while raising the opportunity to establish clinical phenotypes with the goal of predicting long-term complications. In this paper, we critically review the classic and the novel autoantibodies in SjS, analyzing the methods employed for detection, the pathogenic role and the wide spectrum of clinical phenotypes.

Biomarkers of lymphoma in Sjögren's syndrome: what's the latest?

INTRODUCTION

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease standing in the crossroads of autoimmunity and lymphomagenesis, characterized by chronic B-cell hyperactivity and ectopic lymphoid tissue neoformation, potentially driving lymphoid malignant transformation. Lymphoma development is considered the most serious complication of pSS.

AREAS COVERED: “

Old-classical" biomarkers (clinical, serological, hematological, and histological) validated in the past are analyzed under the perspective of recently published research. Biomarkers that have emerged during the last decade are subdivided to "old-new" and "newly proposed-novel" ones, including biomarkers pathophysiologically related to B-cell differentiation, lymphoid organization, and immune responses, identified in serum and tissue, both at genetic and protein level. Upcoming new imaging biomarkers, promising for further patient stratification, are also analyzed.

EXPERT OPINION

Salivary gland enlargement and cryoglobulinemia still remain the best validated "classical-old" biomarkers for lymphoma development. Though new biomarkers still need to be validated, some can be used for the identification of high-risk patients long before lymphoma diagnosis, some might be more relevant in distinct age subgroups, while others have an added value in the assessment of lymphoma remission or relapse. Future development of composite indices integrating old and recently proposed biomarkers could contribute to a more precise lymphoma prediction model.

Sjögren Syndrome: New Insights in the Pathogenesis and Role of Nuclear Medicine

In the last years, new insights into the molecular basis of rheumatic conditions have been described, which have generated particular interest in understanding the pathophysiology of these diseases, in which lies the explanation of the diversity of clinical presentation and the difficulty in diagnostic and therapeutic approaches. In this review, we focus on the new pathophysiological findings for Sjögren syndrome and on the derived new SPECT and PET radiopharmaceuticals to detect inflammation of immunological origin, focusing on their role in diagnosis, prognosis, and the evaluation of therapeutic efficacy.

Role of tertiary lymphoid organs in the regulation of immune responses in the periphery

Tertiary lymphoid organs (TLOs) are collections of immune cells resembling secondary lymphoid organs (SLOs) that form in peripheral, non-lymphoid tissues in response to local chronic inflammation. While their formation mimics embryologic lymphoid organogenesis, TLOs form after birth at ectopic sites in response to local inflammation resulting in their ability to mount diverse immune responses. The structure of TLOs can vary from clusters of B and T lymphocytes to highly organized structures with B and T lymphocyte compartments, germinal centers, and lymphatic vessels (LVs) and high endothelial venules (HEVs), allowing them to generate robust immune responses at sites of tissue injury. Although our understanding of the formation and function of these structures has improved greatly over the last 30 years, their role as mediators of protective or pathologic immune responses in certain chronic inflammatory diseases remains enigmatic and may differ based on the local tissue microenvironment in which they form. In this review, we highlight the role of TLOs in the regulation of immune responses in chronic infection, chronic inflammatory and autoimmune diseases, cancer, and solid organ transplantation.

Mono/polyclonal free light chains as challenging biomarkers for immunological abnormalities

Free light chain (FLC) kappa (k) and lambda (λ) consist of low molecular weight proteins produced in excess during immunoglobulin synthesis and secreted into the circulation. In patients with normal renal function, over 99% of FLCs are filtered and reabsorbed. Thus, the presence of FLCs in the serum is directly related to plasma cell activity and the balance between production and renal clearance. FLCs are bioactive molecules that may exist as monoclonal (m) and polyclonal (p) FLCs. These have been detected in several body fluids and may be key indicators of ongoing damage and/or illness. International guidelines now recommend mFLC for screening, diagnosis and monitoring multiple myeloma and other plasma cell dyscrasias. In current clinical practice, FLCs in urine indicate cast nephropathy and other renal injury, whereas their presence in cerebrospinal fluid is important for identifying central nervous system inflammatory diseases such as multiple sclerosis. Increased pFLCs have also been detected in various conditions characterized by B cell activation, i.e., chronic inflammation, autoimmune disease and HCV infection. Monitoring the coronavirus (COVID-19) pandemic by analysis of salivary FLCs presents a significant opportunity in clinical immunology worthy of scientific pursuit.

Labial Gland Mesenchymal Stem Cell Derived Exosomes-Mediated miRNA-125b Attenuates Experimental Sjogren's Syndrome by Targeting PRDM1 and Suppressing Plasma Cells

The pathogenesis of the prototypical chronic autoimmune disorder primary Sjögren syndrome (pSS) has been thought to be B-cell-centric, based on serum autoantibodies, the increased risk of B cell lymphoma, and altered B cell subsets in patients with pSS. Over the last 10 years, therapies targeting B cells have been investigated for pSS; however, current evidence for the efficacy of B cell targeted therapies in pSS is still sparse. Mesenchymal stem cells (MSCs) might represent a promising strategy for cell therapy of autoimmune diseases via regulation of immune cells. MSC-released exosomes carry various bioactive molecules and thus have been studied in MSC-based therapy. The newly discovered labial gland MSCs (LGMSCs) have exhibited enhanced performance. Herein, we aimed to determine the effects of LGMSC-derived exosomes (LGMSC-Exos) on the symptoms of a mouse model of pSS and their regulatory effect and mechanism on B cell subsets. In vivo, treatment of the spontaneous mouse model of pSS with LGMSC-Exos resulted in reduced inflammatory infiltration and restored saliva secretion in salivary glands. In vitro, coculture of LGMSC-Exos with peripheral blood mononuclear cells of patients with pSS markedly reduced the proportions of CD19⁺CD20^-CD27⁺CD38⁺ plasma cells among peripheral blood mononuclear cells. Further investigations provided evidence that LGMSC-Exo-derived microRNA-125b affected plasma cells of pSS by directly binding to its target gene, PRDM1 (PR domain zinc finger protein 1, also known as BLIMP1), which might be developed as a target to treat pSS. Overall, these findings provided a possible exploitable therapeutic target in pSS and provide new insights into the potential therapeutic application of exosomes in pSS and other disease mediated by B-cells.

Digital image analysis of intraepithelial B-lymphocytes to assess lymphoepithelial lesions in salivary glands of Sjögren's syndrome patients

OBJECTIVE

Salivary glands of primary SS (pSS) patients characteristically harbour periductal infiltrates, in which lymphoepithelial lesions (LELs) can develop. LELs are composed of hyperplastic ductal epithelium with infiltrating lymphocytes and may assist in the challenging diagnostic process of pSS. As manual identification of LELs remains difficult, we aimed to identify LELs by using an objective digital image analysis (DIA) algorithm that detects intraepithelial lymphocytes.

METHODS

A virtual triple-staining technique developed for this study was used to count intraepithelial lymphocytes in consecutive slides stained for CD3 (T-lymphocytes), high-molecular-weight cytokeratin (hmwCK) (striated ducts) and CD20 (B-lymphocytes) in labial and parotid gland biopsies in a diagnostic cohort of 109 sicca patients. Patients were classified as having pSS or non-SS according to the ACR-EULAR classification criteria.

RESULTS

T-lymphocytes were detected in almost all analysed ducts of pSS and non-SS sicca patients, whereas intraepithelial B-lymphocytes were present in 59-68% of labial and parotid gland biopsies of pSS patients, against only 2-3% of patients classified as non-SS. Intraepithelial B-lymphocytes were found in almost all striated ducts with hyperplasia (LELs). Remarkably, ∼25% of analysed striated ducts without hyperplasia of pSS patients also contained B-lymphocytes (precursor-LELs). Furthermore, presence of intraepithelial B-lymphocytes was associated with clinical parameters of pSS (i.e. serology).

CONCLUSION

The presence of intraepithelial B-lymphocytes in salivary gland biopsies of sicca patients is a clear indicator of pSS and can be used as an objective alternative to LEL scoring. Therefore, identification of B-lymphocyte-containing ducts should be added to the diagnostic histopathological work-up of patients suspected of pSS.

Recent Advances of Salivary Gland Biopsy in Sjögren's Syndrome

Sjögren's syndrome (SS) is a chronic, systemic, inflammatory autoimmune disease characterized by lymphocyte proliferation and progressive damage to exocrine glands. The diagnosis of SS is challenging due to its complicated clinical manifestations and non-specific signs. Salivary gland biopsy plays an important role in the diagnosis of SS, especially with anti-Sjögren's syndrome antigen A (SSA) and anti-SSB antibody negativity. Histopathology based on biopsy has clinical significance for disease stratification and prognosis evaluation, such as risk assessment for the development of non-Hodgkin's lymphoma. Furthermore, histopathological changes of salivary gland may be implicated in evaluating the efficacy of biological agents in SS. In this review, we summarize the histopathological features of salivary gland, the mechanism of histopathological changes and their clinical significance, as well as non-invasive imaging techniques of salivary glands as a potential alternative to salivary gland biopsy in SS.

Autoantibodies in Sjögren's syndrome and its classification criteria

Sjögren's syndrome (SS) is a systemic autoimmune disease characterized by immune-mediated injury of exocrine glands. Extensive lymphocytic infiltrates may contribute to the destruction and loss of secretory function of glands. B-cell hyperactivity is a key feature of the disease resulting in the production of a diverse array of autoantibodies in these patients. Although not specific for SS, anti-Ro/SSA and anti-La/SSB antibodies have been useful biomarkers for disease classification and diagnosis. During recent years, novel autoantibodies have been discovered in SS. In this review, we summarize the historical role and clinical relevance that autoantibodies have played in the classification criteria of Sjögren's syndrome, discuss laboratory aspects in antibody detection and review the role of novel autoantibodies in predicting particular stages of the disease, clinical phenotypes and long-term complications.

Cellular and molecular diversity in Sjogren's syndrome salivary glands: Towards a better definition of disease subsets

Primary Sjögren's syndrome (pSS) is a highly heterogeneous disease in terms of clinical presentation ranging from a mild disease localised to the salivary and lacrimal glands, to multiorgan complications of various degrees of severity, finishing with the evolution, in around 5% of pSS patients, to B cell lymphomas most commonly arising in the inflamed salivary glands. Currently, there are poor positive or negative predictors of disease evolution able to guide patient management and treatment at early stages of the diseases. Recent understanding of the pathogenic mechanisms driving immunopathology in pSS, particularly through histological and transcriptomic analysis of minor and parotid salivary gland (SG) biopsies, has highlighted a high degree of cellular and molecular heterogeneity of the inflammatory lesions but also allowed the identification of clusters of patients with similar underlying SG immunopathology. In particular, patients presenting with high degrees of B/T cell infiltration and the formation of ectopic lymphoid structures (ELS) in the SG have been associated, albeit with conflicting results, with higher degree of disease severity and enhanced risk of lymphoma evolution, suggesting that a dysregulated adaptive immune response plays a key role in driving disease manifestations in pSS. Recent data from randomised clinical trials with novel biological therapies in pSS have also highlighted the potential role of SG immunopathology and molecular pathology in stratifying patients for trial inclusion as well as assessing proof of mechanisms in longitudinal SG biopsies before and after treatment. Although significant progress has been made in the understanding of disease pathogenesis and heterogeneity through cellular and molecular SG pathology, further work is needed to validate their clinical utility in routine clinical settings and in randomised clinical trials.

Fibroblasts as immune regulators in infection, inflammation and cancer

In chronic infection, inflammation and cancer, the tissue microenvironment controls how local immune cells behave, with tissue-resident fibroblasts emerging as a key cell type in regulating activation or suppression of an immune response. Fibroblasts are heterogeneous cells, encompassing functionally distinct populations, the phenotypes of which differ according to their tissue of origin and type of inciting disease. Their immunological properties are also diverse, ranging from the maintenance of a potent inflammatory environment in chronic inflammation to promoting immunosuppression in malignancy, and encapsulating and incarcerating infectious agents within tissues. In this Review, we compare the mechanisms by which fibroblasts control local immune responses, as well as the factors regulating their inflammatory and suppressive profiles, in different tissues and pathological settings. This cross-disease perspective highlights the importance of tissue context in determining fibroblast-immune cell interactions, as well as potential therapeutic avenues to exploit this knowledge for the benefit of patients with chronic infection, inflammation and cancer.

Histopathology, salivary flow and ultrasonography of the parotid gland: three complementary measurements in primary Sjögren's syndrome

OBJECTIVE

The involvement of salivary glands in primary Sjögren's syndrome (pSS) can be assessed in different ways: histopathology, salivary flow and ultrasonography. To understand the relative value of these different approaches, it is crucial to understand the relationship between them. As we routinely perform these three modalities in the parotid gland for disease evaluation, our aim was to investigate the construct validity between these modalities in one and the same gland.

METHODS

Consecutive sicca patients underwent a multidisciplinary diagnostic work-up including parotid gland biopsy, collection of parotid gland-specific saliva and parotid gland ultrasonography. Patients who were classified as pSS according to the ACR-EULAR criteria were included. Construct validity was assessed using Spearman's correlation coefficients.

RESULTS

The 41 included pSS patients completed a full work-up within mean time interval of 2.6 months. Correlations between histopathological features and stimulated parotid salivary flow were fair (ρ=-0.123 for focus score, and ρ=-0.259 for percentage of CD45+ infiltrate). Likewise, poor correlations were observed between stimulated parotid salivary flow and parotid ultrasonography (ρ=-0.196). Moderate to good associations were found between the histopathological items focus score and percentage of CD45+ infiltrate, with parotid ultrasound scores (total ultrasound score: ρ = 0.510 and ρ = 0.560; highest for homogeneity: ρ = 0.574 and ρ = 0.633).

CONCLUSION

Although pSS associated ultrasonographic findings did correlate with histopathological features, the three modalities that evaluate salivary gland involvement assess different (or at best partly related) constructs. Therefore, histopathology, salivary flow and ultrasonography are complementary measurements and cannot directly replace each other in the work-up of pSS.

Autoimmunity in dry eye disease - An updated review of evidence on effector and memory Th17 cells in disease pathogenicity

The classic Th1/Th2 dogma has been significantly reshaped since the subsequent introduction of several new T helper cell subsets, among which the most intensively investigated during the last decade is the Th17 lineage that demonstrates critical pathogenic roles in autoimmunity and chronic inflammation - including the highly prevalent dry eye disease. In this review, we summarize current concepts of Th17-mediated disruption of ocular surface immune homeostasis that leads to autoimmune inflammatory dry eye disease, by discussing the induction, activation, differentiation, migration, and function of effector Th17 cells in disease development, highlighting the phenotypic and functional plasticity of Th17 lineage throughout the disease initiation, perpetuation and sustention. Furthermore, we emphasize the most recent advance in Th17 memory formation and function in the chronic course of dry eye disease, a major area to be better understood for facilitating the development of effective treatments in a broader field of autoimmune diseases that usually present a chronic course with recurrent episodes of flare in the target tissues or organs.

Focal lymphocytic sialadenitis and ectopic germinal centers in oral reactive lesions and primary Sjögren's syndrome: a comparative study

Focal lymphocytic sialadenitis (FLS), an important diagnostic criterion for Sjögren's syndrome (SS) diagnosis, can also be observed when assessing minor salivary gland (mSG) biopsies from healthy asymptomatic individuals (non-SS patients). Fifty cases of primary SS (pSS group) and 31 cases of oral reactive lesions (non-SS non-sicca group) containing also typical FLS features, were assessed by morphological and immunohistochemical (CD10, CD23 and Bcl-6) analysis, aiming at the detection of GCs. All pSS cases showed FLS with focus score (FS) ≥ 1. In the non-SS non-sicca group, 12, 10 and 9 cases showed FLS with FS ≥ 1, FLS with FS < 1 and FLS associated with chronic sclerosing sialadenitis with FS < 1, respectively. The morphological analysis revealed similar frequency of GCs in pSS (20%) and non-SS non-sicca group (19%). The area (p = 0.052) and largest diameter (p = 0.245) of GCs were higher in pSS than non-SS non-sicca group. The FS and number of foci were significantly higher in pSS than non-SS non-sicca group with FS < 1. Immunohistochemistry confirmed all morphological findings (GCs showing CD23 and Bcl-6 positivity, with variable CD10 expression) and additionally in 3 and 1 cases of the pSS and non-SS non-sicca group, respectively. Moreover, another 6 and 2 cases of the pSS and non-SS non-sicca group with FS ≥ 1, respectively, showed positivity only for CD23. FLS can also be observed when assessing oral reactive lesions, which showed similar frequency of GCs with those found in pSS patients. Further studies, including functional analysis of lymphocytic populations and GCs in FLS, are encouraged.

The Transcriptome of Paired Major and Minor Salivary Gland Tissue in Patients With Primary Sjögren's Syndrome

Background

While all salivary glands (SGs) can be involved in primary Sjögren's syndrome (pSS), their respective role in pathogenesis remains unclear. Our objective was to assess immunopathway activation in paired parotid and labial gland tissue from biopsy-positive and biopsy-negative pSS and non-SS sicca patients.

Methods

Paraffin-embedded, paired parotid and labial salivary gland tissue and peripheral blood mononuclear cells were obtained from 39 pSS and 20 non-SS sicca patients. RNA was extracted, complementary DNA libraries were prepared and sequenced. For analysis of differentially expressed genes (DEGs), patients were subdivided based on fulfillment of ACR-EULAR criteria and histopathology.

Results

With principal component analysis, only biopsy-positive pSS could be separated from non-SS sicca patients based on SG gene expression. When comparing the transcriptome of biopsy-positive pSS and biopsy-negative non-SS sicca patients, 1235 and 624 DEGs (FDR<0.05, log2FC<-1 or >1) were identified for parotid and labial glands, respectively. The number of DEGs between biopsy-negative pSS and non-SS sicca patients was scarce. Overall, transcript expression levels correlated strongly between parotid and labial glands (R2 = 0.86, p-value<0.0001). Gene signatures present in both glands of biopsy-positive pSS patients included IFN-α signaling, IL-12/IL-18 signaling, CD3/CD28 T-cell activation, CD40 signaling in B-cells, DN2 B-cells, and FcRL4+ B-cells. Signature scores varied considerably amongst pSS patients.

Conclusion

Transcriptomes of paired major and minor SGs in pSS were overall comparable, although significant inter-individual heterogeneity in immunopathway activation existed. The SG transcriptome of biopsy-negative pSS was indistinguishable from non-SS sicca patients. Different patterns of SG immunopathway activation in pSS argue for personalized treatment approaches.

Metformin as a Treatment Strategy for Sjögren's Syndrome

Sjögren's syndrome (SS), a chronic inflammatory disease involving the salivary and lacrimal glands, presents symptoms of sicca as well as systemic manifestations such as fatigue and musculoskeletal pain. Only a few treatments have been successful in management of SS; thus treatment of the disease is challenging. Metformin is the first-line agent for type 2 diabetes and has anti-inflammatory potential. Its immunomodulatory capacity is exerted via activation of 5' adenosine monophosphate-activated protein kinase (AMPK). Metformin inhibits mitochondrial respiratory chain complex I which leads to change in adenosine mono-phosphate (AMP) to adenosine tri-phosphate (ATP) ratio. This results in AMPK activation and causes inhibition of mammalian target of rapamycin (mTOR). mTOR plays an important role in T cell differentiation and mTOR deficient T cells differentiate into regulatory T cells. In this manner, metformin enhances immunoregulatory response in an individual. mTOR is responsible for B cell proliferation and germinal center (GC) differentiation. Thus, reduction of B cell differentiation into antibody-producing plasma cells occurs via downregulation of mTOR. Due to the lack of suggested treatment for SS, metformin has been considered as a treatment strategy and is expected to ameliorate salivary gland function.

B cells as target for immunotherapy in rheumatic diseases - current status

This mini-review is a short overview of different therapeutical strategies targeting B cells in systemic autoimmune rheumatic diseases, mainly: rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and primary Sjogren Syndrome (pSS). Many strategies and their rationale are discussed in this review: B cells' depletion (anti-CD20, anti-CD22), long-lived plasma cells depletion (anti-CD19, anti-CD27, anti-CD38 and anti-CD138), changing activation of B cells (anti-BAFF) and inhibiting proteasomes in plasma cells (bortezomib). The past successful therapies and less successful are shown, and the possible reasons for failures are discussed.

Identification of the key genes and pathways involved in B cells in primary Sjögren' s syndrome

Primary Sjögren’ s syndrome (pSS) is a relatively common autoimmune disease, which mainly involves the exocrine glands, causing dry eye, dryness of mouth, fatigue and pain in the joints, thus severely affecting the normal lives of patients. B cell populations are considered to play an important role in their pathogenesis and pSS patients are generally characterized by exhibiting biological signs of B cell activation. Moreover, another important characterized change in the peripheral blood of pSS patients is found to be the decreased number of circulating memory B cells. However, the mechanisms underlying the B cell activation and the decreased level of circulating memory B cells in pSS patients are still unclear. Therefore, we identified key genes and pathways involved in B cells in pSS through a combination of several bioinformatic approaches including Cell-type Identification By Estimating Relative Subsets Of RNA Transcripts (CIBERSORT) and weighted gene co-expression network analysis (WGCNA) using gene expression data of pSS patients and controls from an open database Gene Expression Omnibus (GEO). The results may provide some novel insights into the pathogenesis of pSS. Moreover, we constructed and validated a diagnostic model for pSS by using the expression patterns of these key genes, which may assist clinicians in diagnosing pSS.

New frontiers in precision medicine for Sjogren's syndrome

Introduction: Sjögren's syndrome is a unique systemic autoimmune disease, placed in the center of systemic autoimmunity and at the crossroads of autoimmunity and lymphoproliferation. The diverse clinical picture of the disease, the inefficacy of current biologic treatments, and the co-existence with lymphoma conferring to the patients' morbidity and mortality force the scientific community to review disease pathogenesis and reveal the major implicated cellular and molecular elements.Areas covered: Biomarkers for early diagnosis, prediction, stratification, monitoring, and targeted treatments can serve as a tool to interlink and switch from the clinical phenotyping of the disease into a more sophisticated classification based on the underlying critical molecular pathways and endotypes. Such a transition may define the establishment of the so-called precision medicine era in which patients' management will be based on grouping according to pathogenetically related biomarkers. In the current work, literature on Sjogren's syndrome covering several research fields including clinical, translational, and basic research has been reviewed.Expert opinion: The perspectives of clinical and translational research are anticipated to define phenotypic clustering of high-risk pSS patients and link the clinical picture of the disease with fundamental molecular mechanisms and molecules implicated in pathogenesis.

The Involvement of Innate and Adaptive Immunity in the Initiation and Perpetuation of Sjögren's Syndrome

Sjogren’s syndrome (SS) is a chronic autoimmune disease characterized by the infiltration of exocrine glands including salivary and lachrymal glands responsible for the classical dry eyes and mouth symptoms (sicca syndrome). The spectrum of disease manifestations stretches beyond the classical sicca syndrome with systemic manifestations including arthritis, interstitial lung involvement, and neurological involvement. The pathophysiology underlying SS is not well deciphered, but several converging lines of evidence have supported the conjuncture of different factors interplaying together to foster the initiation and perpetuation of the disease. The innate and adaptive immune system play a cardinal role in this process. In this review, we discuss the inherent parts played by both the innate and adaptive immune system in the pathogenesis of SS.

Reproducibility of minor salivary gland biopsy reports in Sjögren's syndrome and its correlation with disease biomarkers

INTRODUCTION/OBJECTIVE

Sjögren's syndrome (SS) is a systemic autoimmune disease that is challenging to diagnose. Although minor salivary gland biopsy (MSGB) is a useful ancillary study, different factors make its interpretation difficult. Also, the significance of distinct histopathological findings is unknown. We aimed to determine the concordance between pathologists and rheumatologists in interpreting the MSGB results, as well as the correlation between MSGB findings, paraclinical features, and SS diagnosis.

METHODS

This descriptive retrospective study reviewed medical charts from 998 individuals from a single center where MSGBs had been performed. Rheumatologists interpreted biopsy reports from pathologists, and interobserver variability was calculated. Logistic regression using immunological parameters and histological findings was performed.

RESULTS

We included 998 patients with a median age of 55 years (45-64 years); the majority of patients were females (n = 934, 93.6%). Chisholm and Mason's scoring system was the most frequently used scale (55.1%). There was a good correlation between pathologists and rheumatologists for diagnosing SS using MSGB findings (Cohen's kappa 0.91). We observed a strong association between interstitial plasmocytes and SS (OR 24, 95% CI 9.09-64.94, p = 0).

CONCLUSION

The MSGB is an essential tool for the diagnosis of SS. Although different factors may negatively affect its reproducibility, histological findings, such as interstitial plasmocytes, may predict the risk of developing SS. Key Points • We provide information based on 998 patients with suspected SS diagnosis. • Chisholm and Mason's scale is the most frequently used compared to Greenspan's and Tarpley's scales. • There is good correlation between pathologists and rheumatologists for the diagnosis of SS using MSGB.

Follicular helper T cells and follicular regulatory T cells in the immunopathology of primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease, characterized by lymphocytic infiltration into exocrine glands, which causes dry eyes, dry mouth, and systemic damage. Although the precise etiology of pSS is not clear yet, highly activated B cells, abundant anti-SSA/Ro, and anti-SSB/La autoantibodies are the hallmarks of this disease. Follicular helper T cells (Tfh), a subset of CD4⁺ T cells, with cell surface receptors PD-1 and CXCR5, express ICOS, transcription factor Bcl-6, and a cytokine IL-21. These cells help in the differentiation of B cells into plasma cells and stimulate the formation of germinal center (GC). Previous studies have demonstrated abundant Tfh cells in the peripheral blood and salivary glands (SGs) of the patients with pSS, correlated with extensive lymphocytic infiltration of the SGs and high disease activity scores. Patients with pSS who are treated with abatacept (CTLA-4 Ig) show fewer circulating Tfh cells, reduced expression of ICOS, and lower disease activity scores. Recently identified follicular regulatory T (Tfr) cells, a subset of regulatory T cells, control the function of Tfh cells and the GC reactions. Here, we summarize the observed alterations in Tfh and Tfr cell numbers, activation state, and circulating subset distribution in pSS. Our goal is to improve the understanding of the roles of Tfh and Tfr cells (surface marker expression, cytokine production, and transcription factors) in the pathogenesis of pSS, thus contributing to the identification of candidate therapeutic agents for this disease.

Fingolimod reduces salivary infiltrates and increases salivary secretion in a murine Sjögren's model

Sjögren's Syndrome (SjS) is a chronic, systemic autoimmune disease causing xerostomia, xerophthalmia, and systemic symptoms. The principal pathological finding in SjS is the accumulation of lymphocytes in exocrine glandular tissue and elsewhere, leading to secretory dysfunction and other abnormalities. A rational therapeutic approach might be to interfere with lymphocyte migration to the periphery from central lymphoid tissues. We thus examined in an animal model of SjS the effects of Fingolimod (FTY720, Gilenya™), which interferes with migration of lymphocytes to peripheral sites. Fingolimod induces sequestration of lymphocytes in lymphoid organs by altering lymphocyte expression of sphingosine-1-phosphate receptors. In the C57Bl/6. NOD.Aec1Aec2 (AEC) model of SjS, Fingolimod reduced circulating T and B cell numbers. Treatment of AEC mice with Fingolimod increased salivary output and decreased the size of salivary gland infiltrates. Oral Fingolimod thus merits further consideration in the management of SjS in humans.

Pathogenetic Mechanisms Implicated in Sjögren's Syndrome Lymphomagenesis: A Review of the Literature

Sjögren's Syndrome (SS) is a chronic autoimmune disorder characterized by focal mononuclear cell infiltrates that surround the ducts of the exocrine glands, impairing the function of their secretory units. Compared to other autoimmune disorders, SS is associated with a notably high incidence of non-Hodgkin lymphoma (NHL) and more frequently mucosa associated lymphoid tissue (MALT) lymphoma, leading to increased morbidity and mortality rates. High risk features of lymphoma development include systemic extraepithelial manifestations, low serum levels of complement component C4 and mixed type II cryoglobulinemia. The discrimination between reactive and neoplastic lymphoepithelial lesion (LEL) is challenging, probably reflecting a continuum in the evolution from purely inflammatory lymphoid infiltration to the clonal neoplastic evolution. Early lesions display a predominance of activated T cells, while B cells prevail in severe histologic lesions. This strong B cell infiltration is not only a morphologic phenomenon, but it is also progressively associated with the presence of ectopic germinal centers (GCs). Ectopic formation of GCs in SS represents a complex process regulated by an array of cytokines, adhesion molecules and chemokines. Chronic antigenic stimulation is the major driver of specific B cell proliferation and increases the frequency of their transformation in the ectopic GCs and marginal zone (MZ) equivalents. B cells expressing cell surface rheumatoid factor (RF) are frequently detected in the salivary glands, suggesting that clonal expansion might arise from antigen selection of RF-expressing B cells. Abnormal stimulation and incomplete control mechanisms within ectopic lymphoid structures predispose RF MZ like cells to lymphoma development. Immunoglobulin recombination, somatic mutation and isotype switching during B cell development are events that may increase the translocation of oncogenes to immunoglobulin loci or tumor suppressor gene inactivation, leading to monoclonal B cell proliferation and lymphoma development. Concerning chronic antigenic stimulation, conclusive data is so far lacking. However immune complexes containing DNA or RNA are the most likely candidates. Whether additional molecular oncogenic events contribute to the malignant overgrowth remains to be proved.

Efficacy and safety of iguratimod on patients with primary Sjögren's syndrome: a randomized, placebo-controlled clinical trial

Objective: To evaluate the clinical efficacy and safety of iguratimod for the treatment of primary Sjögren's syndrome (pSS) and explore its possible mechanism of action.Method: We conducted a randomized, placebo-controlled clinical trial in 66 pSS patients. Patients were randomized in a 2:1 ratio to receive oral iguratimod for 24 weeks or matching placebo. The primary endpoint was the EULAR Sjögren's Syndrome Patient Reported Index (ESSPRI). Secondary endpoints included mental discomfort visual analogue scale (VAS) score, patient global assessment (PGA), EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI), Schirmer's test values, unstimulated whole salivary flow, erythrocyte sedimentation rate (ESR), and immunoglobulin G (IgG). The proportions of B cells in peripheral blood and levels of serum B-cell activating factor (BAFF) were measured at baseline and week 24 in the iguratimod group. All adverse events were recorded during the trial period.Results:ESSPRI improved more in the iguratimod than in the placebo group (p = 0.016). Mental discomfort VAS score, PGA, Schirmer's test, ESR, and IgG also improved more in the iguratimod than in the placebo group (all p < 0.05). Adverse events were reported 13.6% of the iguratimod group. Levels of BAFF and proportions of plasma cells in patients decreased significantly after iguratimod treatment. The proportions of peripheral plasma cells had positive correlations with both serum IgG and BAFF.Conclusion: Iguratimod improved some dryness symptoms and disease activity in pSS patients, and reduced the level of BAFF and percentage of plasma cells over 24 weeks. Iguratimod seems to be an effective and safe treatment for pSS.

Biologic therapy in Sjögren's syndrome

Sjögren's syndrome (SS) is a chronic autoimmune disease with complex and diverse clinical manifestations. It is characterized by lymphocyte infiltration of exocrine glands such as the salivary gland and lacrimal gland leading to insufficient secretion of the gland, manifested as dry mouth and dry eyes. In addition, it can involve extraglandular organs and cause systemic damage. The pathogenesis of SS is still unclear. At present, symptomatic treatment is the mainstay and there is a lack of effective therapy. With the development of molecular pathways underlying the pathogenesis of SS, more and more novel biological agents are used to treat SS. We summarized and analyzed the existing evidences on the efficacy of biological treatment of SS and their targets. Analysis of the efficacy of biological therapy and improvement of treatment strategies can help to give full play to its therapeutic advantages.

Minor salivary gland biopsy: Its role in the classification and prognosis of Sjögren's syndrome

Sjögren's syndrome (SS) is an autoimmune disorder characterized by mononuclear cell infiltration in the exocrine glands, which leads to sicca syndrome (xerostomia and xerophthalmia). The etiology of SS is unknown, but multiple environmental factors (infectious, hormonal and stress-related), as well as genetic factors, may play a role in its pathogenesis. The diagnosis of SS is complex considering its clinical and paraclinical parameters may not be very specific. The minor salivary gland biopsy (MSGB) has undoubtedly become crucial for classifying and determining the prognosis of SS. The three main different classification systems for its interpretation have been described by Chisholm and Mason, Greenspan and Daniels, and Tarpley. However, this invasive procedure has variable sensitivity and specificity as well as low reproducibility. The use of additional methods, such as skin biopsy, imaging techniques, and serum/salivary biomarkers, may be combined with current methods to develop a bioscore that could increase diagnostic performance. In this review, we summarized the main pathological findings in SS and the prognosis of patients with SS according to the biopsy results.

Contributions of Major Cell Populations to Sjögren's Syndrome

Sjögren’s syndrome (SS) is a female dominated autoimmune disease characterized by lymphocytic infiltration into salivary and lacrimal glands and subsequent exocrine glandular dysfunction. SS also may exhibit a broad array of extraglandular manifestations including an elevated incidence of non-Hodgkin’s B cell lymphoma. The etiology of SS remains poorly understood, yet progress has been made in identifying progressive stages of disease using preclinical mouse models. The roles played by immune cell subtypes within these stages of disease are becoming increasingly well understood, though significant gaps in knowledge still remain. There is evidence for distinct involvement from both innate and adaptive immune cells, where cells of the innate immune system establish a proinflammatory environment characterized by a type I interferon (IFN) signature that facilitates propagation of the disease by further activating T and B cell subsets to generate autoantibodies and participate in glandular destruction. This review will discuss the evidence for participation in disease pathogenesis by various classes of immune cells and glandular epithelial cells based upon data from both preclinical mouse models and human patients. Further examination of the contributions of glandular and immune cell subtypes to SS will be necessary to identify additional therapeutic targets that may lead to better management of the disease.

Epigenetically quantified immune cells in salivary glands of Sjögren's syndrome patients: a novel tool that detects robust correlations of T follicular helper cells with immunopathology

OBJECTIVE

To investigate whether epigenetic cell counting represents a novel method to quantify immune cells in salivary glands of patients with different forms of Sjögren's and sicca syndrome and to capture immunopathology and potentially aid in diagnosis.

METHODS

DNA from frozen salivary gland tissue sections of sicca patients was used for bisulphite conversion of demethylated DNA cytosine residues, followed by cell-specific quantitative PCR to calculate cell percentages in relation to total tissue cell numbers as quantified by housekeeping gene demethylation. The percentages of epigenetically quantified cells were correlated to RNA expression of matched salivary gland tissue and histological and clinical parameters.

RESULTS

The percentages of epigenetically quantified CD3, CD4, CD8, T follicular helper (Tfh) cells, FoxP3+ regulatory T cells and B cells were significantly increased in the salivary glands of patients with SS. Unsupervised clustering using these percentages identified patient subsets with an increased lymphocytic focus score and local B cell hyperactivity and classifies patients different from conventional classification criteria. In particular, Tfh cells were shown to strongly correlate with the expression of CXCL13, lymphocytic focus scores, local B cell hyperactivity and anti-SSA positivity.

CONCLUSION

Epigenetic cell counting is a promising novel tool to objectively and easily quantify immune cells in the labial salivary gland of sicca patients, with a relatively small amount of tissue needed. In view of the potential of this technique to include a huge number of (cell-specific) biomarkers, this opens up new standardized ways of salivary gland analysis with high relevance for patient classification, understanding of immunopathology and monitoring of drug responses in clinical trials.

Rationale for CD40 pathway blockade in autoimmune rheumatic disorders

CD40 and its ligand CD40L (CD154) belong to the tumor necrosis factor receptor superfamily and are expressed by a variety of immune and non-immune cells. CD40L plays a central role in co-stimulation and regulation of the immune response via activation of cells expressing CD40. Imbalance of the CD40-CD40L co-stimulatory pathway has been reported in many autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, and Sjögren's syndrome, thus supporting its role in the breach of immune tolerance that is typical of these diseases. Targeting CD40-CD40L signalling might represent a novel therapeutic option for several autoimmune disorders.