Genome-wide association study identifies Sjögren's risk loci with functional implications in immune and glandular cells

Sjögren's disease is a complex autoimmune disease with twelve established susceptibility loci. This genome-wide association study (GWAS) identifies ten novel genome-wide significant (GWS) regions in Sjögren's cases of European ancestry: CD247, NAB1, PTTG1-MIR146A, PRDM1-ATG5, TNFAIP3, XKR6, MAPT-CRHR1, RPTOR-CHMP6-BAIAP6, TYK2, SYNGR1. Polygenic risk scores yield predictability (AUROC = 0.71) and relative risk of 12.08. Interrogation of bioinformatics databases refine the associations, define local regulatory networks of GWS SNPs from the 95% credible set, and expand the implicated gene list to >40. Many GWS SNPs are eQTLs for genes within topologically associated domains in immune cells and/or eQTLs in the main target tissue, salivary glands.

Radiographic features in 2D imaging as predictors for justified CBCT examinations of canine-induced root resorption

OBJECTIVES

This retrospective observational study aimed to evaluate the diagnostic accuracy of two-dimensional radiographs on canine-induced root resorption (CIRR) in lateral incisors and identify predictors of CIRR in patients with impacted maxillary canines (IMC).

METHODS

Ninety-nine patients aged 9-17 years, with 156 IMCs, were included in the study. All had CBCT-volumes and two-dimensional radiographs consisting of at least one panoramic radiograph. Two radiologists jointly viewed all cases twice. First, radiographic features related to the IMC and possible CIRR were recorded from two-dimensional radiographs. Then, CIRR was determined from CBCT and according to position and extension classified as mild, moderate and severe.

RESULTS

CIRRs was detected in 80% of lateral incisors (mild: 45%; moderate: 44%; severe: 11%). The sensitivity was generally low at mild and moderate cut-offs (29 and 29%), and somewhat higher for severe (50%). Corresponding specificities were 48%, 63% and 68%. Canine cusp-tip superimposing the lateral incisor's middle third and root/crown ratio >1 was positively associated with mild CIRR, with an odds ratio (OR) of 3.8 and 6.7, respectively. In addition, the root development stage was positively associated with moderate/severe CIRR when the canine root was nearly or fully developed (OR = 3.1).

CONCLUSIONS

The diagnostic accuracy of two-dimensional radiographs was inadequate for detecting CIRR amongst patients referred for CBCT examinations. Based on our results, none of the suggested two-dimensional radiographic features could predict moderate/severe CIRR except for root development stage. IMC in a later stage of root development seems to be associated with a higher risk of moderate/severe CIRR.

Understanding Fatigue in Sjögren's Syndrome: Outcome Measures, Biomarkers and Possible Interventions

Sjögren’s syndrome (SS) is an autoimmune disease affecting the salivary and lacrimal glands. Symptoms range from dryness to severe extra-glandular disease involving manifestations in the skin, lungs, nervous system, and kidney. Fatigue occurs in 70% of patients, characterizing primary SS (pSS) and significantly impacting the patient’s quality of life. There are some generic and specific instruments used to measure fatigue in SS. The mechanisms involved with fatigue in SS are still poorly understood, but it appears fatigue signaling pathways are more associated with cell protection and defense than with pro-inflammatory pathways. There are no established pharmacological treatment options for fatigue in pSS. So far, exercise and neuromodulation techniques have shown positive effects on fatigue in pSS. This study briefly reviews fatigue in pSS, with special attention to outcome measures, biomarkers, and possible treatment options.

Genetic and clinical basis for two distinct subtypes of primary Sjögren's syndrome

OBJECTIVES

Clinical presentation of primary Sjögren's syndrome (pSS) varies considerably. A shortage of evidence-based objective markers hinders efficient drug development and most clinical trials have failed to reach primary endpoints.

METHODS

We performed a multicentre study to identify patient subgroups based on clinical, immunological and genetic features. Targeted DNA sequencing of 1853 autoimmune-related loci was performed. After quality control, 918 patients with pSS, 1264 controls and 107 045 single nucleotide variants remained for analysis. Replication was performed in 177 patients with pSS and 7672 controls.

RESULTS

We found strong signals of association with pSS in the HLA region. Principal component analysis of clinical data distinguished two patient subgroups defined by the presence of SSA/SSB antibodies. We observed an unprecedented high risk of pSS for an association in the HLA-DQA1 locus of odds ratio 6.10 (95% CI: 4.93, 7.54, P=2.2×10-62) in the SSA/SSB-positive subgroup, while absent in the antibody negative group. Three independent signals within the MHC were observed. The two most significant variants in MHC class I and II respectively, identified patients with a higher risk of hypergammaglobulinaemia, leukopenia, anaemia, purpura, major salivary gland swelling and lymphadenopathy. Replication confirmed the association with both MHC class I and II signals confined to SSA/SSB antibody positive pSS.

CONCLUSION

Two subgroups of patients with pSS with distinct clinical manifestations can be defined by the presence or absence of SSA/SSB antibodies and genetic markers in the HLA locus. These subgroups should be considered in clinical follow-up, drug development and trial outcomes, for the benefit of both subgroups.

Salivary Gland Ultrasonography in Sjögren's Syndrome: A European Multicenter Reliability Exercise for the HarmonicSS Project

Objectives: Salivary gland ultrasonography (SGUS) is increasingly applied for the management of primary Sjögren's syndrome (pSS). This study aims to: (i) compare the reliability between two SGUS scores; (ii) test the reliability among sonographers with different levels of experience.

Methods: In the reliability exercise, two four-grade semi-quantitative SGUS scoring systems, namely De Vita et al. and OMERACT, were tested. The sonographers involved in work-package 7 of the HarmonicSS project from nine countries in Europe were invited to participate. Different levels of sonographers were identified on the basis of their SGUS experience and of the knowledge of the tested scores. A dedicated atlas was used as support for SGUS scoring.

Results: Twenty sonographers participated in the two rounds of the reliability exercise. The intra-rater reliability for both scores was almost perfect, with a Light's kappa of 0.86 for the De Vita et al. score and 0.87 for the OMERACT score. The inter-rater reliability for the De Vita et al. and the OMERACT score was substantial with Light's Kappa of 0.75 and 0.77, respectively. Furthermore, no significant difference was noticed among sonographers with different levels of experience.

Conclusion: The two tested SGUS scores are reliable for the evaluation of major salivary glands in pSS, and even less-expert sonographers could be reliable if adequately instructed.

Juvenile Sjögren's Syndrome: Clinical Characteristics With Focus on Salivary Gland Ultrasonography

OBJECTIVE

Juvenile Sjögren's syndrome (SS) is a rare, poorly defined, and possibly underdiagnosed condition affecting children and adolescents. The aim of this study was to characterize symptoms and clinical findings of juvenile SS and to explore the clinical application of major salivary gland ultrasonography (SGUS) in patients with juvenile SS.

METHODS

A cross-sectional multicenter study recruited patients with disease onset until age 18 years (n = 67). Disease characteristics were recorded, and unstimulated whole sialometry and SGUS examination of the parotid and submandibular salivary glands were performed.

RESULTS

The female:male ratio was 58:9. The mean age at first symptom was 10.2 years and 12.1 years at diagnosis. Ocular and oral symptoms were noted in 42 of 67 patients (63%) and 53 of 66 patients (80%), respectively. The American-European Consensus Group or American College of Rheumatology/European League Against Rheumatism classification criteria for primary SS were fulfilled by 42 of 67 patients (63%). Pathologic SGUS findings were observed in 41 of 67 patients (61%); 26 of 41 SGUS+ patients (63%) fulfilled primary SS criteria. Salivary gland enlargements/parotitis were noted in 37 of 58 patients and were nonsignificantly associated with SGUS+ status (P = 0.066). The mean levels of saliva were 5.6 ml/15 minutes in SGUS- patients compared to 3.3 ml/15 minutes in the SGUS+ patients (P = 0.049). A total of 36 of 41 SGUS+ patients (88%) were anti-Ro/La+ compared to 14 of 26 SGUS- patients (54%) (P = 0.001). In addition, 24 of 39 SGUS+ patients (62%) were positive for rheumatoid factor (RF), whereas only 5 of 25 SGUS- patients (20%) were RF+ (P = 0.001).

CONCLUSION

Juvenile SS is characterized by a large spectrum of clinical symptoms and findings. Several glandular and extraglandular parameters such as hyposalivation, swollen salivary glands, and autoantibodies are associated with pathologic SGUS findings.

Assessment of major salivary gland ultrasonography in Sjögren's syndrome. A comparison between bedside and post-examination evaluations

OBJECTIVES

Major salivary gland ultrasonography (SGUS) is a suitable diagnostic tool in Sjögren's syndrome (SS). We aimed to determine the more representative gland, projection and format most applicable for reproducible image analysis.

METHODS

One investigator performed SGUS in patients with SS. Parotid and submandibular glands were examined in longitudinal and transverse planes and evaluated bedside using a simplified scoring system (0-3). Longitudinal and transverse images and videos of all glands were stored and later evaluated/graded by three investigators, at two time-points. Agreement was calculated using intraclass correlation coefficient (ICC).

RESULTS

The ICC for static image and video scoring compared to bedside evaluation ranged from 0.131 to 0.882. Average ICC for longitudinal/transverse image was 0.667/0.662, and 0.683/0.510 for longitudinal/transverse video. Interobserver reliability was good to excellent (0.81-0.94). Intraobserver reliability scores ranged from fair to excellent (0.46-0.96). The correlation between image and video evaluations of all modalities and examiners was good to excellent (0.614-0.904). The best mean ICC was found for the longitudinal projection of the left parotid gland (0.861) and the lowest mean ICC was for the transverse projection of the left submandibular gland (0.66).

CONCLUSIONS

Our study indicates a trend favouring longitudinal video of the parotid gland as preferred projection, gland and storage format.

Current concepts on Sjögren's syndrome - classification criteria and biomarkers

Sjögren's syndrome is a lymphoproliferative disease with autoimmune features characterized by mononuclear cell infiltration of exocrine glands, notably the lacrimal and salivary glands. These lymphoid infiltrations lead to dryness of the eyes (keratoconjunctivitis sicca), dryness of the mouth (xerostomia), and, frequently, dryness of other surfaces connected to exocrine glands. Sjögren's syndrome is associated with the production of autoantibodies because B-cell activation is a consistent immunoregulatory abnormality. The spectrum of the disease extends from an organ-specific autoimmune disorder to a systemic process and is also associated with an increased risk of B-cell lymphoma. Current treatments are mainly symptomatic. As a result of the diverse presentation of the syndrome, a major challenge remains to improve diagnosis and therapy. For this purpose an international set of classification criteria for primary Sjögren's syndrome has recently been developed and validated and seems well suited for enrolment in clinical trials. Salivary gland biopsies have been examined and histopathology standards have been developed, to be used in clinical trials and patient stratification. Finally, ultrasonography and saliva meet the need of non-invasive imaging and sampling methods for discovery and validation of disease biomarkers in Sjögren's syndrome.

Long-term follow-up in primary Sjögren's syndrome reveals differences in clinical presentation between female and male patients

Background

Despite men being less prone to develop autoimmune diseases, male sex has been associated with a more severe disease course in several systemic autoimmune diseases. In the present study, we aimed to investigate differences in the clinical presentation of primary Sjögren’s syndrome (pSS) between the sexes and establish whether male sex is associated with a more severe form of long-term pSS.

Methods

Our study population included 967 patients with pSS (899 females and 68 males) from Scandinavian clinical centers. The mean follow-up time (years) was 8.8 ± 7.6 for women and 8.5 ± 6.2 for men (ns). Clinical data including serological and hematological parameters and glandular and extraglandular manifestations were compared between men and women.

Results

Male patient serology was characterized by more frequent positivity for anti-Ro/SSA and anti-La/SSB (p = 0.02), and ANA (p = 0.02). Further, men with pSS were more frequently diagnosed with interstitial lung disease (p = 0.008), lymphadenopathy (p = 0.04) and lymphoma (p = 0.007). Conversely, concomitant hypothyroidism was more common among female patients (p = 0.009).

Conclusions

We observe enhanced serological responses and higher frequencies of lymphoma-related extraglandular manifestations in men with pSS. Notably, lymphoma itself was also significantly more common in men. These observations may reflect an aggravated immune activation and a more severe pathophysiological state in male patients with pSS and indicate a personalized managing of the disease due to the influence of the sex of patients with pSS.

Salivary gland ultrasound abnormalities in primary Sjögren's syndrome: consensual US-SG core items definition and reliability

Objectives

Ultrasonography (US) is sensitive for detecting echostructural abnormalities of the major salivary glands (SGs) in primary Sjögren’s syndrome (pSS). Our objectives were to define selected US-SG echostructural abnormalities in pSS, set up a preliminary atlas of these definitions and evaluate the consensual definitions reliability in both static and acquisition US-SG images.

Methods

International experts in SG US in pSS participated in consensus meetings to select and define echostructural abnormalities in pSS. The US reliability of detecting these abnormalities was assessed using a two-step method. First 12 experts used a web-based standardised form to evaluate 60 static US-SG images. Intra observer and interobserver reliabilities were expressed in κ values. Second, five experts, who participated all throughout the study, evaluated US-SG acquisition interobserver reliability in pSS patients.

Results

Parotid glands (PGs) and submandibular glands (SMGs) intra observer US reliability on static images was substantial (κ > 0.60) for the two main reliable items (echogenicity and homogeneity) and for the advised pSS diagnosis. PG inter observer reliability was substantial for homogeneity. SMGs interobserver reliability was moderate for homogeneity (κ = 0.46) and fair for echogenicity (κ = 0.38). On acquisition images, PGs interobserver reliability was substantial (κ = 0.62) for echogenicity and moderate (κ = 0.52) for homogeneity. The advised pSS diagnosis reliability was substantial (κ = 0.66). SMGs interobserver reliability was fair (0.20< κ ≤ 0.40) for echogenicity and homogeneity and either slight or poor for all other US core items.

Conclusion

This work identified two most reliable US-SG items (echogenicity and homogeneity) to be used by US-SG trained experts. US-PG interobserver reliability result for echogenicity is in line with diagnosis of pSS.

Impaired salivary gland activity in patients with autoimmune polyendocrine syndrome type I

Autoimmune polyendocrine syndrome type I (APS-I) is a severe disease caused by mutations in the autoimmune regulator (AIRE) gene. We hypothesized that salivary gland dysfunction could be a possible unexplored component of these patients and here aimed to investigate salivary and lachrymal symptoms in the Norwegian cohort of APS-I patients (N = 41) and the aetiology behind it. Sicca symptoms and possible corresponding underlying factors were assessed by subjective reports combined with objective measures of saliva and tear flow, serological testing, immune fluorescence microscopy, ultrasonography and searching for putative autoantibodies in the salivary glands. In addition, defensin and anti-defensin levels were analysed in patients and compared with healthy controls. Our results indicate mild salivary and/or lachrymal gland dysfunction manifesting in low saliva or tear flow in a total of 62% of APS-I patients. Serum IgG from 9 of 12 patients bound to targets in salivary gland biopsy slides, although the specificity and pattern of binding varied. There was no reactivity against known Sjögren-associated autoantigens in sera from APS-I patients using quantitative methods, but 11% were ANA positive by immunofluorescence microscopy. We identified several putative autoantigens in one patient, although none of these were verified as APS-I specific. We conclude that impaired salivary gland activity is part of the clinical picture of APS-I and our findings could indicate an autoimmune aetiology. We further show that APS-I patients have an altered antimicrobial signature in both sera and saliva, which requires further investigations.

Low Protein A20 in Minor Salivary Glands is Associated with Lymphoma in Primary Sjögren's Syndrome

Patients with primary Sjögren's syndrome (pSS) have an increased risk of developing lymphomas, particularly the subtype mucosa-associated lymphoid tissue (MALT) lymphoma. Chronic antigen stimulation and increased activation of nuclear factor-κB (NF-κB) are important factors for the pathogenesis of MALT lymphomas. Protein A20 is an inhibitor of NF-κB. A recent study of pSS-associated MALT lymphomas identified potential functional abnormalities in the TNFAIP3 gene, which encodes protein A20. The present study aimed to assess protein A20 by immunohistochemistry (IHC) in minor salivary glands (MSGs) and lymphoma tissue sections of patients with pSS and investigate a potential association with lymphoma development. Protein A20 staining in lymphocytes was scored in four categories (0 = negative, 1 = weak, 2 = moderate and 3 = strong). For statistical purposes, these scores were simplified into negative (scores 0-1) and positive (scores 2-3). We investigated associations between protein A20-staining, focus scores, germinal centre (GC)-like structures and monoclonal B-cell infiltration in MSGs. MSG protein A20 staining was weaker in pSS patients with lymphomas than in those without lymphomas (P = 0.01). Weak protein A20 staining was also highly associated with a lack of GC formation (P < 0.01). Finally, weaker A20 staining was observed in the majority of pSS-associated MALT lymphoma tissues. In conclusion, we found absent or weak protein A20 immunoreactivity in MSGs of patients with pSS with lymphomas. This finding indicates that protein A20 downregulation in lymphocytes might be a mechanism underlying lymphoma genesis in patients with pSS.

Antibodies against carbamylated proteins are present in primary Sjögren's syndrome and are associated with disease severity

Objectives

Herein, we investigate the presence and prognostic value of autoantibodies against carbamylated proteins (anti-CarP) in the serum of patients with primary Sjögren's syndrome (pSS).

Patients and methods

Serum levels of anti-CarP antibodies were measured in Norwegian patients with pSS (n=78) and corresponding controls (n=74) using ELISA and analysed in relation with exocrine gland function, degree of salivary gland inflammation, signs of ectopic germinal centre (GC) formation and immunological markers. For univariate comparisons, the Mann–Whitney U test and χ² or Fisher's exact tests were used. Correlations were assessed with Spearman's rank testing. Multivariate regression analyses were used to assess the effect of anti-CarP positivity on clinical manifestations.

Results

Of the patients with pSS, 27% were positive for anti-CarP IgG antibodies. Levels of anti-CarP correlated positively with total IgG, IgM, rheumatoid factor and β2-microglobulin. Importantly, after adjusting for confounding factors, patients positive for anti-CarP had significantly higher focus score. Furthermore, positive anti-CarP status coincided with 9.2-fold higher odds of having developed GC-like structures in the minor salivary glands. As a patient group considered having worse disease outcome, individuals with ectopic GC-like structures also presented with significantly higher levels of anti-CarP antibodies.

Conclusions

Presence of anti-CarP in patients with pSS is strongly associated with increased focal lymphocytic infiltration, formation of ectopic GC-like structures in minor salivary glands, and diminished salivary gland function. Even taking into consideration our relatively small cohort we believe that anti-CarP antibodies offer new possibilities for identifying patients with more active disease and at risk of developing additional comorbidity.

High fidelity between saliva proteomics and the biologic state of salivary glands defines biomarker signatures for primary Sjögren's syndrome

OBJECTIVE

Dependence on invasive procedures for classification of patients with Sjögren's syndrome (SS) hampers timely diagnosis and suitable patient followup. The aim of this study was to recapitulate the diagnosis of SS through noninvasive means and to define the biologic state of SS patients' salivary glands.

METHODS

Using a 187-plex capture antibody-based assay, salivary proteomic biomarker profiles were generated from patients with primary SS, patients with rheumatoid arthritis, and asymptomatic controls. Discriminant function analyses and Gene Ontology-based network analyses allowed data analyses with a reductionist approach and with a focus on systems biology.

RESULTS

Characterized by significant changes in 61 and 55 proteins, respectively, the salivary proteome of SS patients appeared profoundly altered compared to that of individuals without SS. On this basis, 4-plex and 6-plex biomarker signatures, both including interleukin-4 (IL-4), IL-5, and clusterin, achieved accurate prediction of an individual's group membership for at least 94% of cases. Of note, all misclassified SS patients presented with ectopic germinal center-like structures. Systematic inference of biologic meaning identified SS-related protein patterns delineating B cell-dominated immune responses, macrophage differentiation, and signs of T cell chemotaxis. In addition, proteomic Multi-Analyte Profiles provided insight about proteins related to collagen, cytokine, and growth factor synthesis as well as lipid transport.

CONCLUSION

The SS-related molecular landscape conveyed by saliva showed great congruence with histopathologic features found in SS and advances understanding of this disease at a molecular level. Such salivary biomarker signatures harbor great potential for improving timeliness of SS diagnosis and enabling suitable patient followup.

Diagnostic utility of major salivary gland ultrasonography in primary Sjögren's syndrome

OBJECTIVES

To investigate major salivary gland ultrasonography (US) in relation to symptoms and findings of oral and ocular dryness, and autoimmune disease, for potential use in diagnosis and follow-up of patients with primary Sjögren's syndrome (pSS).

METHODS

Patients with pSS were recruited from the Department of Rheumatology, Haukeland University Hospital. The parotid and submandibular salivary glands were examined by US using a simplified scoring system for glandular homogeneity and hypoechogenic areas. Scans were graded on a scale 0-3, grades 0-1 considered corresponding to normal/non-specific changes and grades 2-3 to pathological changes. Sicca symptoms of the mouth and eyes, salivary gland capacity, tear secretion, minor salivary gland inflammation, serum autoantibodies, and fatigue were also investigated.

RESULTS

US was performed in 97 patients. Oral and ocular sicca symptoms correlated with US score and decreased saliva levels. Fatigue VAS correlated with oral sicca symptoms but was inversely correlated with age. Patients with normal/non-specific US findings tended to be older than patients with pathological US findings. US score correlated with unstimulated and stimulated salivary secretion and tear secretion. Minor salivary gland inflammation correlated with major salivary gland US findings, and lymphoid organisation, germinal centre (GC)-like structures, in the minor salivary gland tissue biopsies was seemingly related to US pathology. Serum autoantibodies against Ro/SSA and/or La/SSB were associated with US pathology.

CONCLUSIONS

US findings in major salivary glands correlate with subjective and objective oral and ocular items as well as systemic autoimmune features of pSS. US represents a useful imaging tool for diagnostics and follow-up of pSS.

Sjögren's syndrome: an update on epidemiology and current insights on pathophysiology

Primary Sjögren's syndrome (pSS) is an autoimmune chronic inflammatory disorder affecting 0.2% to 3.0% of the population, with a 9:1 female to male ratio. Features are oral and ocular dryness, local and systemic autoantibody production, and progressive focal mononuclear cell infiltration in the affected salivary and lacrimal glands. Lymphoma is the most severe complication of pSS, occurring in 4% to 5% of patients. Genetic studies identified an association with HLA and susceptibility genes in cytokine genes and genes involved in B-cell differentiation. Genetic variations may help explain why disease manifestations differ among patients and supports the hypothesis of certain distinct disease phenotypes.

Association of genes in the NF-κB pathway with antibody-positive primary Sjögren's syndrome

Primary Sjögren's syndrome (SS) is a systemic autoimmune inflammatory disease characterized by focal lymphocytic infiltrates in the lachrymal and salivary glands and autoantibodies against the SSA/Ro and SSB/La antigens. Experimental studies have shown an activation of NF-κB in primary SS. NF-κB activation results in inflammation and autoimmunity and is regulated by inhibitory and activating proteins. Genetic studies have shown an association between multiple autoimmune diseases and TNFAIP3 (A20) and TNIP1 (ABIN1), both repressors of NF-κB and of IKBKE (IKKε), which is an NF-κB activator. The aim of this study was to analyse single nucleotide polymorphisms (SNPs) in the IKBKE, NFKB1, TNIP1 and TNFAIP3 genes for association with primary SS. A total of 12 SNPs were genotyped in 1105 patients from Scandinavia (Sweden and Norway, n = 684) and the UK (n = 421) and 4460 controls (Scandinavia, n = 1662, UK, n = 2798). When patients were stratified for the presence of anti-SSA and/or anti-SSB antibodies (n = 868), case-control meta-analysis found an association between antibody-positive primary SS and two SNPs in TNIP1 (P = 3.4 × 10(-5) , OR = 1.33, 95%CI: 1.16-1.52 for rs3792783 and P = 1.3 × 10(-3) , OR = 1.21, 95%CI: 1.08-1.36 for rs7708392). A TNIP1 risk haplotype was associated with antibody-positive primary SS (P = 5.7 × 10(-3) , OR = 1.47, 95%CI: 1.12-1.92). There were no significant associations with IKBKE, NFKB1 or TNFAIP3 in the meta-analysis of the Scandinavian and UK cohorts. We conclude that polymorphisms in TNIP1 are associated with antibody-positive primary SS.

Predictors for the development of non-Hodgkin lymphoma in primary Sjögren's syndrome

Sjögren's syndrome (SS) is a complex autoimmune disease with multi-organ involvement. Its most serious complication is the development of non-Hodgkin lymphoma (NHL). In cohorts of unselected patients with long observation, this lifetime risk is estimated to be 5 to 15%, or approximately 20 times increased risk compared to the general population. Being able to identify patients prone to malignancy would significantly aid in the process of customised treatment and strategy for follow-up. Among the established predictors for lymphoma development in SS, we recognize recurrent or permanent swelling of major salivary glands (SG), lymphadenopathy, cryoglobulinemia, splenomegaly, low complement levels of C4 and C3, lymphopenia, skin vasculitis or palpable purpura, M-component in serum or urine, peripheral neuropathy, glomerulonephritis and elevated beta2-microglobulin. More recent suggestions include some genetic factors, CD4 lymphocytopenia, and ectopic germinal center-like structures in minor SG biopsies. Despite these predictors, there remains a need for defining algorithms for NHL screening and patient follow-up in SS.

Lymphoid organisation in labial salivary gland biopsies is a possible predictor for the development of malignant lymphoma in primary Sjögren's syndrome

Objective

The development of non-Hodgkin's lymphoma (NHL) confers a high risk of mortality in primary Sjögren's syndrome (pSS) patients, but the sensitivity and specificity of proposed lymphoma predictors are insufficient for practical use. The performance of lymphoid organisation in the form of germinal centre (GC)-like lesions was evaluated in labial salivary gland biopsies taken at pSS diagnosis as a potential lymphoma-predicting biomarker.

Methods

Labial salivary gland tissue biopsies available from two Swedish pSS research cohorts (n=175) were re-evaluated by light microscopy in a blind study in order to identify GC-like structures as a sign of ectopic lymphoid tissue formation and organisation. A linkage study was performed with the Swedish Cancer Registry for lymphoma identification. The risk of developing NHL in GC-positive patients in comparison with GC-negative patients was evaluated using Kaplan–Meier statistics and log-rank test. Associations between GC-like structures and clinical and/or laboratory disease markers were also determined using χ² or Fisher's exact tests.

Results

At diagnosis, 25% of pSS patients had GC-like structures in their salivary glands. Seven of the 175 patients studied (14% GC+ and 0.8% GC−) developed NHL during 1855 patient-years at risk, with a median onset of 7 years following the initial diagnostic salivary gland biopsy. Six of the seven patients had GC-like structures at diagnosis; the remaining patient was GC negative at the time of diagnosis (p=0.001).

Conclusions

The detection of GC-like structures by light microscopy in pSS diagnostic salivary biopsies is proposed as a highly predictive and easy-to-obtain marker for NHL development. This allows for risk stratification of patients and the possibility to initiate preventive B-cell-directed therapy.

Implications of long-term medication of oral steroids and antimalarial drugs in primary Sjögren's syndrome

BACKGROUND

Immunomodulating drugs are commonly used in treating patients with autoimmune diseases but with very different outcomes. We aimed to investigate differences in cytokine and autoantibody levels with regard to patient characteristics in patients with primary Sjögren's syndrome (pSS) receiving oral steroids or antimalarial drugs (AM) after a longer period of time.

METHODS

Serum samples from 141 patients fulfilling the revised EU-US criteria and 99 healthy controls were analysed for 25 cytokines and 8 autoantibodies.

RESULTS

AM-patients had lowered levels of IL-5, IL-10, IL-13 and IFN-γ, though non-significantly. Use of prednisolone was associated with reduced levels of IL-15, IL-2, IL-4, IL-12p40, TNF-α, MIP-1α and MIP-1β (p<0.05), and a trend towards decreased levels of IL-1RA and IL-1β was observed. No associations were seen between AM and antibody levels. Significantly higher protein levels of anti-Ro-52 and anti-Ro-60 were observed in the patients taking prednisolone (p<0.05). The proportion of patients positive for anti-Ro-52 and anti-La-48 did not differ significantly in the groups taking and not taking prednisolone, but a difference was seen for anti-Ro-60 (p<0.05).

CONCLUSIONS

Prednisolone is a potent anti-inflammatory and immunosuppressive drug commonly used in autoimmune diseases. Our study shows that oral steroids are associated with reduced levels of several pro-inflammatory cytokines, but increased levels of pSS specific autoantibodies. The association between steroid use and increased antibody levels is not readily explained by known steroid effects, and should therefore be confirmed in further studies. Lower levels of pro-inflammatory cytokines indicate a beneficial effect of oral steroids in this patient group.

Salivary glands of primary Sjögren's syndrome patients express factors vital for plasma cell survival

INTRODUCTION

The presence of circulating Ro/SSA and La/SSB autoantibodies has become an important marker in the classification criteria for primary Sjögren's syndrome (pSS). Plasma cells producing these autoantibodies are mainly high affinity plasma cells originating from germinal centre reactions. When exposed to the right microenvironment these autoimmune plasma cells become long-lived and resistant to immunosuppressive treatment. Since autoimmune plasma cells have been detected in the salivary glands of SS patients, we wanted to investigate if the glandular microenvironment is suitable for plasma cell survival and if glandular residing plasma cells are the long-lived plasma cell subset.

METHODS

Single, double and triple immunohistochemistry as well as immunofluorescence staining was performed on minor salivary gland tissue retrieved from pSS, chronically inflamed and normal subjects.

RESULTS

We detected significant numbers of CD138+, non-proliferating, Bcl-2 expressing plasma cells in the salivary glands of pSS patients with high focus score (FS). Furthermore, we demonstrated that CXCL12 and interleukin (IL)-6 survival factors were highly expressed in pSS salivary gland epithelium and by focal mononuclear infiltrating cells. Notably, adipocytes when present in the salivary gland tissue were an important source of CXCL12. We clearly demonstrate that plasma cells are localised in close proximity to CXCL12 and IL-6 expressing cells and thus that the environment of salivary glands with high FS provide factors vital for plasma cell survival.

CONCLUSIONS

Plasma cells residing in the salivary glands of pSS patients with high FS showed phenotypic characteristics of the long-lived plasma cell subtype. Furthermore, the pSS salivary gland microenvironment provided niches rich in factors vital for plasma cell survival.

Cytokine and autoantibody profiling related to histopathological features in primary Sjogren's syndrome

OBJECTIVE

To investigate a potential correlation between circulating cytokine and autoantibody levels and histopathological features in subgroups of patients with primary SS (pSS).

METHODS

Minor salivary gland biopsies from a cohort of 141 patients fulfilling the American-European consensus classification criteria for pSS were re-examined and grouped according to focus score (FS) and germinal centre (GC) status; serum samples were analysed for autoantibodies, chemokines and cytokines.

RESULTS

Of the 115 available biopsies, 18 (16%) lacked characteristic focal mononuclear cell infiltrates [FS < 1 (FS-)] but patients were positive for Ro/SSA and/or La/SSB. IL-17, IL-1RA, IL-15, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, eotaxin, IFN-alpha and IL-4 levels were significantly increased in the 27 (23%) patients with ectopic GC formation (GC+) in the salivary glands compared with the GC- patients (n = 70). In addition, minor differences in cytokine levels were found when comparing age groups.

CONCLUSION

Degenerative changes observed in the minor salivary glands of patients with pSS may represent 'burned out' inflammation. The elevated levels of IL-4 found in these patients may influence the reduced salivary flow observed in GC+ patients. Increased titres of Th17-associated cytokines, IL-17, IL-1beta and the IL-23 subunit IL-12p40, may indicate a higher activity of these cells in GC+ patients. Differences in cytokine levels may be utilized when sub-grouping the SS patients into disease phases and may consequently have implications for treatment.

Impaired vascular responses to parasympathetic nerve stimulation and muscarinic receptor activation in the submandibular gland in nonobese diabetic mice

Introduction

Decreased vascular responses to salivary gland stimulation are observed in Sjögren's syndrome patients. We investigate whether impaired vascular responses to parasympathetic stimulation and muscarinic receptor activation in salivary glands parallels hyposalivation in an experimental model for Sjögren's syndrome.

Methods

Blood flow responses in the salivary glands were measured by laser Doppler flowmeter. Muscarinic receptor activation was followed by saliva secretion measurements. Nitric oxide synthesis-mediated blood flow responses were studied after administration of a nitric oxide synthase inhibitor. Glandular autonomic nerves and muscarinic 3 receptor distributions were also investigated.

Results

Maximal blood flow responses to parasympathetic stimulation and muscarinic receptor activation were significantly lower in nonobese diabetic (NOD) mice compared with BALB/c mice, coinciding with impaired saliva secretion in nonobese diabetic mice (P < 0.005). Nitric oxide synthase inhibitor had less effect on blood flow responses after parasympathetic nerve stimulation in nonobese diabetic mice compared with BALB/c mice (P < 0.02). In nonobese diabetic mice, salivary gland parasympathetic nerve fibres were absent in areas of focal infiltrates. Muscarinic 3 receptor might be localized in the blood vessel walls of salivary glands.

Conclusions

Impaired vasodilatation in response to parasympathetic nerve stimulation and muscarinic receptor activation may contribute to hyposalivation observed in nonobese diabetic mice. Reduced nitric oxide signalling after parasympathetic nerve stimulation may contribute in part to the impaired blood flow responses. The possibility of muscarinic 3 receptor in the vasculature supports the notion that muscarinic 3 receptor autoantibodies present in nonobese diabetic mice might impair the fluid transport required for salivation. Parasympathetic nerves were absent in areas of focal infiltrates, whereas a normal distribution was found within glandular epithelium.

Trial registration

The trial registration number for the present study is 79-04/BBB, given by the Norwegian State Commission for Laboratory Animals.

Animal models of Sjögren's syndrome

Sjögren's syndrome is an autoimmune, chronic inflammatory disease characterized by focal mononuclear cell infiltration of exocrine tissues, accompanied by loss of secretory function. The pathogenesis of autoimmune diseases is complex and, therefore, difficult to study in vitro. As of today, the role of initiating factors remains obscure, clinical symptoms develop late, and there are no tests for early diagnosis of SS. Hence, the disease is difficult to detect and treat. Animal models may provide insights into the identification of target antigens, narrowing the relevant pathological immune mechanisms, and to study the evolution of tissue pathology. This review summarizes current knowledge on murine strains, both spontaneous and induced models, used to study Sjögren's syndrome. Special attention is paid to the characteristics of different strains regarding their properties to mimic specific aspects or stages of the disease.

Serological implications of germinal center-like structures in primary Sjögren's syndrome

OBJECTIVE

To determine serological implications of germinal center (GC)-like structures in primary Sjögren's syndrome (pSS).

METHODS

Retrospectively, minor salivary gland biopsies (n = 269) with focal lymphoid aggregates corresponding to focus score > 1 were evaluated for the presence of GC-like morphology. Relevant clinical information was obtained from medical records.

RESULTS

Of 269 patients, 169 fulfilled the American-European criteria for pSS. GC-like features were observed in 47/169 (28%) biopsies. In the majority of cases, GC-like lesions were confirmed by CD21-positive follicular dendritic cell networks. Mean inflammatory focus score was significantly higher in GC-positive compared to GC-negative samples (p < 0.001). GC-positive patients had lower mean salivary secretion (p < 0.001) and a higher frequency of patients with unstimulated salivary secretion < or = 1.5 ml/15 min (p < 0.01). In addition, elevated titers of rheumatoid factor, serum anti-Ro/SSA and anti-La/SSB (p < 0.05), and IgG levels > or = 15.3 g/l (p < 0.05) were more common in GC-positive compared to GC-negative. Enlarged salivary glands were observed in 46/163 (28%) patients, but could not be linked to either presence or absence of GC-like features.

CONCLUSION

Inflammatory infiltrates with GC-like morphology were observed in 28% of the investigated patients with pSS, and was particularly noted in patients with higher focus score. The observed serological aberrations in patients with ectopic GC-like structures in the minor salivary glands warrant further prospective studies.

Role of Dendritic Cells in Sjogren's Syndrome

Sjögren's syndrome (SS) is a chronic inflammatory and lymphoproliferative autoimmune disease of unknown aetiology. It is characterised by progressive mononuclear cell infiltration of the salivary and lacrimal glands and a decreased glandular secretion, resulting in dryness of the mouth and eyes (xerostomia and keratoconjunctivitis sicca, respectively). Dendritic cells (DC) are considered to be the most potent antigen-presenting cells. Because of their central role in initiating an immune response while maintaining tolerance, impaired function of these cells might lead to the break of peripheral tolerance and initiation of immune responses to self-antigens. This review will focus on the possible role of DC in SS.

The thymus is a source of B-cell-survival factors-APRIL and BAFF-in myasthenia gravis

The accumulation of B cells in the thymus is a common feature of myasthenia gravis (MG). To understand whether factors enhancing B-cell survival are increased in MG, we studied the expression of APRIL, BAFF and three of their receptors in the thymus. In hyperplastic thymi, macrophages expressed APRIL and BAFF, and germinal-center B cells, BAFF-R. CD138-positive plasma cells were abundant in MG thymi. By contrast, BCMA-positive plasma cells were scarce. The expression of APRIL and BAFF in MG thymi may reflect the establishment of an environment favorable to B-cell survival.

Impaired salivary gland function in NOD mice: Association with changes in cytokine profile but not with histopathologic changes in the salivary gland

OBJECTIVE

To characterize the chronologic disease course and possible interrelationships between salivary gland inflammation, hyposalivation, and cytokine levels in NOD mice, a model for Sjögren's syndrome (SS).

METHODS

NOD mice of different ages were used to mimic different disease stages of SS. Histopathologic findings and rates of salivary secretion were compared between 8-week-old, 17-week-old, and 24-week-old female mice. In addition, 10 cytokines were analyzed in serum and saliva obtained from NOD and BALB/c mice.

RESULTS

In NOD mice, the salivary flow rate did not change between 8 weeks and 17 weeks of age, while a significant decrease in the salivary flow rate occurred between 17 weeks and 24 weeks of age (P < 0.001). In contrast, significant histopathologic changes in the salivary glands occurred before 17 weeks of age. Chronic inflammatory cell infiltrates were characterized by T and B cell infiltration. Interestingly, in one-third of the mice, proliferating cells were observed in the focal infiltrates. Significant changes in the levels of interleukin-2 (IL-2), IL-5, and granulocyte-macrophage colony-stimulating factor in serum, and in the levels of IL-4 and tumor necrosis factor alpha (TNFalpha) in saliva occurred contemporarily with the decrease in salivary flow. Correlation analyses revealed a negative association between salivary secretion and the levels of IL-4, interferon-gamma, and TNFalpha in saliva obtained from NOD mice, while the correlation with inflammatory changes in the glands was consistently weak.

CONCLUSION

Consistent with previous findings, our results indicate at least 2 phases of SS-like disease in NOD mice. Hyposalivation was preceded by inflammatory changes in the salivary glands, whereas abrupt changes in secretion occurred without significant progression of inflammation. Changes in cytokine levels are an indication of the mechanisms involved in the adaptive immune response in the transition from early to overt disease.

Elevated Serum Levels of Soluble E-Cadherin in Patients with Primary Sjogren's Syndrome

The aim of this study was to investigate serum levels of soluble E-cadherin (sE-cadherin) in relation to lymphocytic organization and to characterize the expression of E-cadherin and integrin alphaEbeta7/CD103 in salivary gland epithelium of patients with Sjögren's syndrome (SS). Serum levels of sE-cadherin were significantly increased in SS compared to non-SS and nonsignificantly in germinal centre (GC)+ compared to GC- patients. Membrane-bound E-cadherin was detected on the majority of acinar and ductal epithelial cells in both SS and non-SS. alphaEbeta7/CD103-positive cells were found scattered in focal infiltrates and GC, and in small clusters close to ductal and acinar epithelium at an increased level in SS compared to non-SS. Interestingly, E-cadherin-positive cells were detected randomly dispersed in focal lymphocytic infiltrates in 10/21 patients. By double-labelling, the cells with the E-cadherin-positive component were identified as CD68(+) macrophages. Elevated serum levels of sE-cadherin indicate an increased epithelial cell turnover and shedding, and sE-cadherin deserves further analysis as a potential diagnostic tool for SS.

Distinct profiles of Sjögren's syndrome patients with ectopic salivary gland germinal centers revealed by serum cytokines and BAFF

The formation of ectopic germinal centers (GC) has been described in Sjögren's syndrome (SS), although little is known about the molecular basis of this phenomenon. These structures are a focus of in situ autoantibody production and have been hypothesized to be involved in lymphomagenesis in SS patients. Serum cytokines also play an important role in SS pathogenesis in part via immune dysregulation and may therefore contribute to ectopic GC formation. Herein, highly multiplex cytokine screening of SS patients with (SSGC+) and without (SSGC-) GC formation was done to identify cytokine profiles that correlate with this phenomenon. Serum levels of B-cell activating factor (BAFF) were also screened as a potential biomarker of immune dysregulation in SS and SSGC formation. Univariate analysis demonstrated that serum levels of a broad spectrum of immune and inflammatory modulating cytokines are upregulated in SSGC+ and SSGC- patients relative to unaffected controls IL-1beta, IL-2, IL-6, IL-15, IFN-gamma and CCL4 (MIP-1beta). SSGC+ patients were distinguished from healthy individuals by higher levels of IL-4, IL-10, GM-CSF, IFN-alpha, CCL3 (MIP-1alpha), CCL11 (Eotaxin) and BAFF, while SSGC+ and SSGC- patients differed in CCL2 (MCP-1) expression. Discriminant function analysis (DFA), a multivariate discrimination method that uses observed differences to characterize groups when casual relationships are not well understood, was employed to identify a subset of these biomarkers that maximally discriminate among SSGC+, SSGC- and unaffected individuals. The biomarker having the strongest discriminatory power identified by DFA besides CCL11 (Eotaxin) and IFN-gamma was BAFF. The variables identified by DFA are interdependent and are often of mechanistic significance to the pathologic states they distinguish, suggesting that these factors modulate SS pathology and SSGC formation in a synergistic manner.

Association between circulating levels of the novel TNF family members APRIL and BAFF and lymphoid organization in primary Sjögren's syndrome

B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are members of the tumour necrosis factor superfamily. We have examined circulating BAFF and APRIL in relation to serological deviations and lymphoid organization in the salivary glands of the chronic, autoimmune disorder Sjögren's syndrome. Lymphoid organization in the shape of ectopic germinal centers were detected in 33 of 130 consecutive minor salivary gland biopsies and coincided with increased focus score and elevated levels of serum IgG. Follicular dendritic cell networks, proliferation of mononuclear cells and altered B/T cell ratio also separated the two subgroups. Serum levels of sBAFF and sAPRIL were increased in Sjögren's syndrome compared to healthy blood donors, especially in anti-Ro/La+ patients. Though the differences could not be related to germinal center formation, positive correlations between serum levels of sBAFF and sAPRIL, focus score and IgG denotes their possible role in the disease progression of primary Sjögren's syndrome.

Cellular basis of ectopic germinal center formation and autoantibody production in the target organ of patients with Sjögren's syndrome

OBJECTIVE

To investigate functional properties of the germinal center (GC)-like structures observed in salivary glands of patients with Sjögren's syndrome (SS) and to determine the frequency with which such structures develop.

METHODS

Hematoxylin and eosin-stained sections from 165 minor salivary gland biopsy samples were screened for GC-like structures. Expression of markers for GCs (CD3, CD20, Ki-67, CD35, CD31), adhesion molecules (intercellular adhesion molecule 1, lymphocyte function-associated antigen 1, vascular cell adhesion molecule 1, very late activation antigen 4), chemokines (CXCL13, CCL21, CXCL12), and production of autoantibodies (anti-Ro/SSA and anti-La/SSB) was investigated by immunohistochemistry. Apoptosis was investigated by TUNEL staining.

RESULTS

GC-like structures were observed in 28 of 165 patients (17%). When GCs were defined as T and B cell aggregates with proliferating cells with a network of follicular dendritic cells and activated endothelial cells, such microenvironments were found in all patients in whom structures with GC-like morphology were observed. The defined microenvironments were not found in patients without apparent GC-like structures. The GCs formed within the target tissue showed functional features with production of autoantibodies (anti-Ro/SSA and anti-La/SSB) and apoptotic events (by TUNEL staining), and the local production of anti-Ro/SSA and anti-La/SSB autoantibodies was significantly increased (P = 0.04) in patients with GC development.

CONCLUSION

Lymphoid neogenesis and functional ectopic GC formation take place in salivary glands of a subset of patients with SS. Our data suggest that the ectopic secondary lymphoid follicles contain all elements needed for driving the autoimmune response. Our findings underscore a key role for the target organ in recruitment of inflammatory cells and propagation of the disease process.

Leukocytes infiltrating the submandibular glands of NOD mice express E-cadherin

Sjögren's syndrome [SS] is typified by infiltration of mononuclear cells [MNC] into the salivary and lacrimal glands, although the biological role of these infiltrating cells remains unclear. We report here that E-cadherin, which mediates cell-cell adhesion and regulates differentiation, proliferation, and apoptosis of epithelial cells, is expressed ectopically by MNC in the salivary glands in the NOD mouse model of SS. Flow cytometric analysis of CD45(+)cells from NOD submandibular glands revealed that over 90% express E-cadherin. More detailed phenotypic analyses demonstrated that E-cadherin expression is high (>90%) among mature T cells (CD3(+)), B cells (CD19(+)), NK cells (DX5(+)), and monocyte/macrophages (CD11b(+)) within the infiltrates. Expression of other surface antigens, such as CD90 and CD117, above expected values suggests the presence of immature leukocytes, possibly of the T cell lineage, within the foci. We also present evidence that E-cadherin-expressing T cells in the glands do not exhibit normal proliferative responses to immobilized anti-CD3 antibody. While infiltrating MNC are not likely to be the direct cause of salivary hypofunction, the expression of E-cadherin by these cells may have implications for the progression of disease.