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.

Inflammatory tissue reactions around aseptically loose cemented hip prostheses: A retrieval study of the Spectron EF stem with Reflection All-Poly acetabular cup

The cemented Spectron EF stem in combination with the cemented non‐crosslinked Reflection All‐Poly cup showed a high rate of mid‐term aseptic loosening. However, the failure mechanisms are not fully known. We assessed the inflammatory tissue reactions and wear particles in periprosthetic tissues, implant wear and blood metal ion levels in 28 patients with failed implants. Histological analysis showed a macrophage pre‐dominant pattern with randomly distributed lymphocytes, with various amounts of neutrophils and giant cells. The number of different cell types in the tissue samples from patients in the cup group and in the stem group was similar. Wear particles, mainly ZrO₂, CoCrMo, and polyethylene particles of different sizes and shapes, were associated with macrophages/giant cells, and total particle load/mm² was higher in cases of stem loosening. The Spectron EF stems were heavily worn, abraded, and polished. Stem abrasion correlated with metal ion concentrations in blood. The median polyethylene wear rate of the Reflection cups was 0.23 mm/year. The high proximal roughness of the Spectron EF stem resulted in excessive cement wear during loosening. The resulting inflammatory tissue responses to the degradation products both from the cup and the stem led to massive osteolysis and subsequent implant loosening.

Inflammatory Stratification in Primary Sjögren's Syndrome Reveals Novel Immune Cell Alterations in Patients' Minor Salivary Glands

There is a critical need to deconvolute the heterogeneity displayed by the minor salivary glands of primary Sjögren’s syndrome (pSS) patients. This is challenging primarily because the disease etiology remains unknown. The hypothesis includes that initial events in the disease pathogenesis target the salivary glands, thereby triggering the development of focal infiltrates (≥50 mononuclear cells) and finally germinal center-like structures. However, the proportion of key mononuclear immune cells residing at these sites, in combination with the overall ratio of morphometric tissue atrophy and adipose infiltration within the minor salivary glands (MSG) parenchyma at distinct phases of inflammatory disease establishment and progression have not been quantified in detail. In this cross-sectional study, we intended to address this problem by stratifying 85 patients into mild (S1), moderate (S2), and severe (S3) stages using the Inflammatory severity index. We found that mild (<3%) and marked (≥3%) levels of atrophy were accompanied by the respective levels of adipose infiltration in the non-SS sicca controls (p <0.01), but not in pSS patients. The percentage of adipose infiltration significantly correlated with the age of patients (r = 0.458, p <0.0001) and controls (r = 0.515, p <0.0001). The CD4⁺ T helper cell incidence was reduced in the focal infiltrates of the MSG of S2 patients compared to S1 (p <0.01), and in S2 compared to S1 and S3 combined (p <0.05). CD20⁺ B cells increased from S1 to S3 (p <0.01) and S2 to S3 (p <0.01), meanwhile CD138⁺ plasma cells diminished in S3 patients compared to both S1 and S2 groups combined (p <0.01). The proportion of patients with anti-Ro/SSA⁺, anti-La/SSB⁺, and RF⁺ increased over the course of inflammatory disease progression and they were significantly more common in the S3 group relative to S1 (p <0.05). On the other hand, S2 patients measured a higher mean salivary flow relative to S1 and S3 patients combined (p <0.05). Our results demonstrate how the proposed Inflammatory severity index stratification revealed pathological cell and tissue-associated aberrations in the salivary component over the course of inflammatory progression, and their correlations to clinical outcomes. This could be directly transferred to the optimization of available diagnostic strategies applied for pSS patients.

Gene expression alterations in salivary gland epithelia of Sjögren's syndrome patients are associated with clinical and histopathological manifestations

Sjögren's syndrome (SS) is a complex autoimmune disease associated with lymphocytic infiltration and secretory dysfunction of salivary and lacrimal glands. Although the etiology of SS remains unclear, evidence suggests that epithelial damage of the glands elicits immune and fibrotic responses in SS. To define molecular changes underlying epithelial tissue damage in SS, we laser capture microdissected (LCM) labial salivary gland epithelia from 8 SS and 8 non-SS controls for analysis by RNA sequencing (RNAseq). Computational interrogation of gene expression signatures revealed that, in addition to a division of SS and non-SS samples, there was a potential intermediate state overlapping clustering of SS and non-SS samples. Differential expression analysis uncovered signaling events likely associated with distinct SS pathogenesis. Notable signals included the enrichment of IFN-γ and JAK/STAT-regulated genes, and the induction of genes encoding secreted factors, such as LTF, BMP3, and MMP7, implicated in immune responses, matrix remodeling and tissue destruction. Identification of gene expression signatures of salivary epithelia associated with mixed clinical and histopathological characteristics suggests that SS pathology may be defined by distinct molecular subtypes. We conclude that gene expression changes arising in the damaged salivary epithelia may offer novel insights into the signals contributing to SS development and progression.

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.

Expression of NGAL-specific cells and mRNA levels correlate with inflammation in the salivary gland, and its overexpression in the saliva, of patients with primary Sjögren's syndrome

Salivary gland involvement is a characteristic feature of primary Sjögren's syndrome (pSS), where tissue destruction is mediated by infiltrating immune cells, and may be accompanied by the presence of adipose tissue. Optimally diagnosing this multifactorial disease requires the incorporation of additional routines. Screening for disease-specific biomarkers in biological fluid could be a promising approach to increase diagnostic accuracy. We have previously investigated disease biomarkers in saliva and tear fluid of pSS patients, identifying Neutrophil gelatinase-associated lipocalin (NGAL) as the most upregulated protein in pSS. In the current study, we aimed to explore for the first time NGAL expression at the site of inflammation in the pSS disease target organ. Immunohistochemical staining was conducted on minor salivary gland biopsies from 11 pSS patients and 11 non-SS sicca subjects, targeting NGAL-specific cells. Additional NGAL/PNAd double staining was performed to study NGAL expression in high endothelial venules, known as specialised vascular structures. Moreover, NGAL mRNA expression was measured utilising quantitative real-time polymerase chain reaction (qRT-PCR) on minor salivary gland biopsies from 15 pSS patients and 7 non-SS sicca individuals that served as tissue controls. Our results demonstrated NGAL expression in acinar and ductal epithelium within the salivary gland of pSS patients, where significantly greater levels of acinar NGAL were observed in pSS patients (p < .0018) when compared to non-SS subjects. Also, acinar expression positively correlated with focus score values (r ² = 0.54, p < .02), while ductal epithelial expression showed a negative such correlation (r ² = 0.74, p < .003). Some PNAD⁺ endothelial venules also expressed NGAL. An increase in NGAL staining with increased fatty replacement was also observed in pSS patients. Concurringly, a 27% increase in NGAL mRNA levels were also detected in the minor salivary glands of pSS patients when compared to non-SS tissue control subjects. In conclusion, there is a positive association between increase in NGAL expression and inflammation in the pSS disease target organ, which also coincides with its previously demonstrated upregulation in the saliva of pSS patients. Additional functional analyses are needed to better understand the immunological implications of this potential biomarker.

Acinar adipose tissue infiltration in salivary gland biopsy is associated with kynurenines-Interferon-γ pathway inflammation biomarkers

OBJECTIVES

Assess if kynurenines metabolites are biomarkers of damage at labial salivary gland biopsy (LSGB).

METHODS

This is a cross-sectional study including 99 patients with primary Sjögren's syndrome (AECG 2002 or ACR/EULAR 2017). Kynurenines were measured in plasma using liquid chromatography-tandem mass spectrometry.

RESULTS

95.9% were females, 51±12 years. Most had focal lymphocytic sialadenitis with focus score ≥1 (73.7%, n=73/99). The majority had mild to severe acinar atrophy (70.4%, n=57/81) and adipose infiltration (51.2%, n=39/80). Individuals with adipose infiltration were older (53.49±12.33 vs. 47.51±11.29 years, p=0.016), showed higher frequency of glandular dysfunction and higher kynurenines levels. Schirmer's test ≤ 5 mm/5min was found in 69.2% of individuals with adipose infiltration compared to 41% without (p=0.012) and unstimulated whole salivary flow (UWSF) was found in 87.2% compared to 70% without adipose infiltration (p=0.063). Additionally, individuals with adipose infiltration showed higher kynurenines metabolites compared with those without: quinolinic acid (503.35±193.30 vs. 427.35±285.76 nmol/L, p=0.029), kynurenine (1.99±0.6, 54 vs. 1.61±0.46 μmol/L, p=0.006), kynurenine/tryptophan ratio (KTR) (0.030±0.09 vs. 0.025±0.01, p=0.031) and anthranilic acid (03±4.96 vs. 16.46±5.24 nmol/L, p=0.022).

CONCLUSIONS

Kynurenines are biomarkers of greater adipose infiltration in LSGB and glandular dysfunction suggesting that activation of interferon-γ pathway is involved in the salivary and lacrimal glands damage.

Proteomic and histopathological characterisation of sicca subjects and primary Sjögren's syndrome patients reveals promising tear, saliva and extracellular vesicle disease biomarkers

Background

Mononuclear cell infiltration of exocrine glands, production of Ro/SSA and La/SSB autoantibodies, along with oral and ocular dryness, are characteristic features of primary Sjögren’s syndrome (pSS). Non-SS sicca subjects, an underexplored group in relation to pSS, display similar sicca symptoms, with possible mild signs of inflammation in their salivary glands, yet with no serological detection of autoantibody production. In this study, we investigated inflammatory manifestations in the salivary gland tissue, tear fluid and saliva of non-SS subjects, as compared to pSS patients and healthy individuals.

Methods

Fifteen non-SS, 10 pSS and 10 healthy subjects were included in the analyses. Histological evaluation of salivary gland biopsies was performed. Liquid chromatography-mass spectrometry (LC-MS) was conducted on tear fluid and stimulated whole saliva, and proteomic biomarker profiles were generated. Extracellular vesicle (EVs) isolation and characterisation from both fluids were also combined with LC-MS. The LC-MS data were analysed for quantitative differences between patient and control groups using Scaffold. Database for Annotation, Visualization and Integrated Discovery (DAVID) and Functional Enrichment Analysis Tool (FunRich) were applied for functional analyses.

Results

Histopathological evaluation of salivary gland biopsies showed implications of milder inflammation in non-SS subjects through mononuclear cell infiltration, fibrosis and fatty replacement, as compared to pSS patients. Although unaffected in the non-SS group, upregulation of proinflammatory pathways and proteins involved in ubiquitination (LMO7 and HUWE1) and B cell differentiation (TPD52) were detected in tear fluid of pSS patients. Moreover, overexpression of proteins STOM, ANXA4 and ANXA1, regulating cellular innate and adaptive immunological pathways, were further identified in EVs from tear fluid of pSS patients. Finally, whole saliva and EVs isolated from whole saliva of pSS patients expressed proteins vital for innate MHC class I cellular regulation (NGAL) and T cell activation (CD44).

Conclusions

Non-SS sicca subjects may show implications of mild inflammation in their glandular tissue, while their protein profile was strikingly more similar to healthy controls than to pSS patients. Hence, the tear and salivary biomarkers identified could be implemented as potential non-invasive diagnostic tools that may aid in increasing diagnostic accuracy when evaluating non-SS subjects and pSS patients and monitoring disease progression.

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1961-4) contains supplementary material, which is available to authorized users.

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.

T follicular-like helper cells in the peripheral blood of patients with primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease characterized by exocrine gland dysfunction, mainly causing sicca symptoms. B cells have a prominent role in SS, and the T follicular helper (TFH ) cells provide B cells with survival and specialization signals in germinal centres. Here, we investigate peripheral TFH cells in pSS. Sixteen pSS patients and healthy controls were enrolled in the study, with 13 women and 3 men in each group. Whole blood was collected and separated into PBMC and plasma, followed by cryopreservation. Plasma samples were analysed for Ro52, Ro60 and La48 autoantibodies by indirect ELISA. For flow cytometric analysis, we defined 4 subsets of TFH-like cells within the CD3+ CD4+ CXCR5+ population, namely the ICOS- PD-1- , ICOS- PD-1+ , ICOS+ PD-1- and ICOS+ PD-1+ ("TFH") cells. We also investigated 4 CD19+ B cell subsets, the CD20+ CD27+ CD38- memory B cells, CD20+ CD27+ CD38+ memory B cells, CD20- CD27+ CD38++ CD138- plasmablasts and CD20- CD27+ CD38++ CD138+ plasma cells. We observed higher fractions of ICOS+ PD-1- cells, ICOS+ PD-1+ ("TFH ") cells and plasmablasts in pSS patients compared to controls, and lower frequencies of both types of memory B cells. The number of TFH cells correlated positively with the levels of plasmablasts and plasma cells in the pSS patients, but not in the controls. The pSS patients were stratified according to Ro52/Ro60/La48 serology, and a positive association was found between autoantibody levels and increased level of TFH cells, plasmablasts and plasma cells and lowered levels of memory B cells. We observed a higher response to Ro/La stimulation in pSS patients compared to controls of the memory B cells, although only significantly for the CD38- memory B cells. Overall, a pathological relation between the ICOS+ T follicular-like helper cells and B cells in pSS was observed, but further work should be conducted to explore their overall impact upon disease progression.

Diminished CXCR5 expression in peripheral blood of patients with Sjögren's syndrome may relate to both genotype and salivary gland homing

Genetic investigations of Sjögren's syndrome (SS) have identified a susceptibility locus at p23.3 of chromosome 11, which contains the CXCR5 gene. C-X-C motif chemokine receptor 5 (CXCR5) is a chemokine receptor expressed on B and T cell subsets, and binds the chemotactic ligand C-X-C motif chemokine ligand 13 (CXCL13). In this study we aimed to link the genetic association with functional effects and explore the CXCR5/CXCL13 axis in SS. Expression quantitative trait loci analysis of the 11q23.3 locus was performed using B cell mRNA expression data from genotyped individuals. Lymphocyte surface markers were assessed by flow cytometry, and CXCL13 levels by a proximity extension assay. CXCR5+ and CXCL13+ cells in minor salivary glands were detected using immunohistochemistry. Our results demonstrated that SS-associated genetic polymorphisms affected the expression of CXCR5 (P < 0·01). Notably, a decreased percentage of CXCR5+ cells, with lower CXCR5 expression, was observed for most circulating B and T cell subsets in SS patients, reaching statistical significance in CD19+ CD27+ immunoglobulin (Ig)D+ marginal zone (P < 0·001), CD19+ CD27+ IgD- memory (P < 0·05) and CD27-IgD double-negative (P < 0·01) B cells and CD4+ CXCR3- CCR6+ Th17 cells (P < 0·05). CXCL13 levels were increased in patient plasma (P < 0·001), and immunohistochemical staining revealed expression of CXCL13 and higher numbers of CXCR5+ cells (P < 0·0001) within focal infiltrates and interstitially in salivary glands of SS patients. In conclusion, we link a genetic susceptibility allele for SS to a functional phenotype in terms of decreased CXCR5 expression. The decrease of CXCR5+ cells in circulation was also related to homing of B and T cells to the autoimmune target organ. Therapeutic drugs targeting the CXCR5/CXCL13 axis may be useful in SS.

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.

Integrin α11 is overexpressed by tumour stroma of head and neck squamous cell carcinoma and correlates positively with alpha smooth muscle actin expression

Background

Cancer‐associated fibroblasts (CAFs) were shown to be important for tumour progression in head and neck squamous cell carcinomas (HNSCCs). Their heterogeneity and lack of specific markers is increasingly recognized. Integrin α11 was recently shown to be expressed by CAFs and might serve as a specific CAF marker.

Aim

To investigate integrin α11 expression and its correlation with the expression of a well‐known marker of CAF, alpha smooth muscle actin (α‐SMA), in HNSCC.

Methods

Fresh frozen (FF) and formalin‐fixed paraffin‐embedded (FFPE) samples from healthy volunteers (n = 24), oral lichen planus (OLP) (n = 32) and HNSCC (n = 106) were collected together with clinical data after ethical approval. Immunohistochemistry to detect integrin α11 and α‐SMA was performed on FF and FFPE samples. qPCR for integrin α11 (ITGA11) and α‐SMA(ACTA2) was performed on FF samples. Data were analysed using chi‐square test and Kaplan–Meier survival analysis.

Results

Significantly higher levels of integrin α11 and α‐SMA at both protein and mRNA levels were found in HNSCC vs. normal controls and OLP. A strong correlation was found between integrin α11 and α‐SMA expression, and double staining showed their colocalization. Both integrin α11 and α‐SMA were detected surrounding metastatic islands. Expression of α‐SMA at tumour front but not tumour centre correlated with patient survival.

Conclusion

Integrin α11 was overexpressed in HNSCC stroma and colocalized with α‐SMA. Expression of α‐SMA at tumour front but not tumour centre had prognostic value for survival, pinpointing the importance of assessing tumour front when evaluating stromal molecules as prognostic biomarkers.

Epidemiology of Sjögren's Syndrome-from an Oral Perspective

Oral symptoms are among the most distressing manifestations for patients with Sjögren's syndrome (SS). The feeling of dry mouth is unpleasant, and hyposalivation may contribute to difficulty in speaking, chewing and swallowing and reduced quality of life. Reduced salivary flow increases the risk for dental caries and problems with prosthetic replacement. It seems that SS is not as frequently occurring as previously anticipated. Population-based prevalence studies on primary SS in Europe, conducted on large background populations and in accordance with the AECG criteria, reported of a prevalence of 1-9 cases per 10,000 people. This gives a combined prevalence of nearly 39/100,000 (~0.04 %). The cause of Sjögren's syndrome is even now not fully understood, and the treatment of oral symptoms is still mostly palliative. Hopefully, useful information will appear from the new methods that are now available for genome wide association studies, epigenetics, DNA methylation studies, and proteomics. Similarly, this is anticipated for the immunological side of the story. The interferon signature, the interferon γ/interferon α mRNA ratio, and CXCL13 are among the proposed biomarkers of active disease. In this review, we provide an update on oral aspects of Sjögren's syndrome with emphasis on the latest publications on these topics.

Adipose tissue is prominent in salivary glands of Sjögren's syndrome patients and appears to influence the microenvironment in these organs

A minor salivary gland (SG) biopsy with focal lymphocytic sialadenitis and a focus score of ≥1 is today's widely accepted pathological finding confirming the SG component of Sjögren's syndrome (SS). Adipocytes can occupy a large percentage of the SG area although little is known about their significance in SS lesions. This study aimed to characterise adipose tissue infiltration in labial SG biopsies from 27 SS patients and 28 non-SS sicca controls. Biopsies were evaluated by one oral pathologist and assessed for focus score, acinar atrophy, fatty replacement and non-specific chronic inflammation. Moreover, to explore the SG microenvironment, immunohistochemical staining of paraffin-embedded SG tissue was performed using interleukin-6 (IL-6). The fatty replacement was evident in all SS patients possessing autoantibodies (Ro/SSA and/or La/SSB) as well as a positive SG biopsy (focus score ≥1). Additionally, 62% of SS patients having autoantibodies but a negative biopsy showed fatty infiltration (FI) while non-SS controls demonstrated fatty replacement in only 32% of the cases. Overall, the SS group (mean age 53.0 years) had a significantly higher incidence (p value 0.005) of FI than the non-SS controls (mean age 54.8 years). Interestingly, adipocytes were located in IL-6 rich areas, and IL-6 positive adipocytes were detected. As fat deposition seems to be more recurrent in SGs affected by SS, we propose the assessment of adipose tissue replacement as a helpful tool for diagnostic evaluation in SS. Detection of IL-6 positive adipocytes suggests their involvement in immune reactions. Still, functional studies are needed to investigate the SG microenvironment further.

Non-proliferating plasma cells detected in the salivary glands and bone marrow of autoimmune NOD.B10.H2b mice, a model for primary Sjögren's syndrome

Autoantibody secreting plasma cells (PCs) are essential contributors in the development of autoimmune conditions such as primary Sjögren's syndrome (pSS). Particularly, the long-lived PC subset residing in the bone marrow has shown to continuously produce autoantibodies, whilst remaining unaffected by immunosuppressive treatment. We have previously shown accumulation of potentially long-lived PCs in chronically inflamed salivary glands of pSS patients. In this study, we aimed to characterise the PC compartment in the salivary glands (the target organ for pSS) and bone marrow before the onset of the murine pSS like disease versus advanced diseases progression. Bromodeoxyuridine (BrdU) was incorporated to distinguish the long-lived PCs. Double immunohistochemical staining and immunofluorescence were then conducted on submandibular gland and bone marrow sections from 8- and 40-week-old mice to identify BrdU and CD138. BrdU(+) cells were detected in the submandibular glands of 8-week-old mice, and observed within all focal infiltrates by 40 weeks of age. Most CD138(+) PCs were however BrdU(-) and located predominantly on the periphery of these infiltrates. This observation was verified through immunofluorescence. A comparable staining pattern was observed in the bone marrow of 8- and 40-week-old NOD.B10.H2b mice, where some of the CD138(+) cells also expressed BrdU. Interestingly, megakaryocytes in the bone marrow of NOD.B10.H2b mice were detected in close proximity to CD138(+) cells, illustrating a possible presence of PC survival niches. Our results demonstrate the presence and accumulation of potentially long-lived PCs in NOD.B10.H2b mice as the disease advances.

Changes in the Submandibular Salivary Gland Epithelial Cell Subpopulations During Progression of Sjögren's Syndrome-Like Disease in the NOD/ShiLtJ Mouse Model

Sjögren's syndrome (SS), an autoimmune exocrinopathy, is associated with dysfunction of the secretory salivary gland epithelium, leading to xerostomia. The etiology of SS disease progression is poorly understood as it is typically not diagnosed until late stage. Since mouse models allow the study of disease progression, we investigated the NOD/ShiLtJ mouse to explore temporal changes to the salivary epithelium. In the NOD/ShiLtJ model, SS presents secondary to autoimmune diabetes, and SS disease is reportedly fully established by 20 weeks. We compared epithelial morphology in the submandibular salivary glands (SMG) of NOD/ShiLtJ mice with SMGs from the parental strain at 12, 18, and 22 weeks of age and used immunofluorescence to detect epithelial proteins, including the acinar marker, aquaporin 5, ductal cell marker, cytokeratin 7, myoepithelial cell marker, smooth muscle α-actin, and the basal cell marker, cytokeratin 5, while confirming immune infiltrates with CD45R. We also compared these proteins in the labial salivary glands of human SS patients with control tissues. In the NOD/ShiLtJ SMG, regions of lymphocytic infiltrates were not associated with widespread epithelial tissue degradation; however, there was a decrease in the area of the gland occupied by secretory epithelial cells in favor of ductal epithelial cells. We observed an expansion of cells expressing cytokeratin 5 within the ducts and within the smooth muscle α-actin(+) basal myoepithelial population. The altered acinar/ductal ratio within the NOD/ShiLtJ SMG likely contributes to salivary hypofunction, while the expansion of cytokeratin 5 positive-basal cells may reflect loss of function or indicate a regenerative response.

Peritumoral dermis of squamous cell carcinomas in renal transplant recipients contains less CD11c+ myeloid dendritic cells and FoxP3+ T cells compared to immunocompetent controls

BACKGROUND

Renal transplant recipients (RTR) have an increased risk of developing cutaneous squamous cell carcinomas (SCC). These SCC are often more aggressive than SCC in immunocompetent individuals.

OBJECTIVES

In this comparative study, we analysed the cell composition in the tissue immediately surrounding invasive SCC in immunosuppressed RTR and immunocompetent controls in an effort to further elucidate the role of the local immune system.

METHODS

Morphology and quantity of various dendritic cell (DC) subsets, macrophages and FoxP3+ T cells were analysed by immunohistochemical staining.

RESULTS

The number of CD11c+ myeloid DC and FoxP3+ T cells was significantly reduced in RTR, whereas the number of plasmacytoid DC, Langerhans cells and macrophages was similar in RTR and controls.

CONCLUSIONS

A reduction in CD11c+ mDC in peritumoral dermis in RTR might contribute to impaired immunosurveillance thus giving rise to an increased risk to develop aggressive SCC in these patients.

Ductal epithelial expression of Ro52 correlates with inflammation in salivary glands of patients with primary Sjögren's syndrome

Ro52 is an E3 ubiquitin ligase with a prominent regulatory role in inflammation. The protein is a common target of circulating autoantibodies in rheumatic autoimmune diseases, particularly Sjögren's syndrome (SS). In this study we aimed to investigate the expression of the SS target autoantigen Ro52 in salivary glands of patients with primary Sjögren's syndrome (pSS). Ro52 expression was assessed by immunohistochemical staining of paraffin-embedded and frozen salivary gland biopsies from 28 pSS patients and 19 non-pSS controls from Swedish and Norwegian registries, using anti-human Ro52 monoclonal antibodies. The degree and pattern of staining and inflammation was then evaluated. Furthermore, secreted Ro52 protein was measured in saliva and serum samples from the same individuals through a catch-enzyme-linked immunosorbent assay (ELISA). Ro52 was highly expressed in all the focal infiltrates in pSS patients. Interestingly, a significantly higher degree of Ro52 expression in ductal epithelium was observed in the patients compared to the non-pSS controls (P < 0·03). Moreover, the degree of ductal epithelial expression of Ro52 correlated with the level of inflammation (Spearman's r = 0·48, P < 0·0120). However, no secreted Ro52 protein could be detected in serum and saliva samples of these subjects. Ro52 expression in ductal epithelium coincides with degree of inflammation and is up-regulated in pSS patients. High expression of Ro52 might result in the breakage of tolerance and generation of Ro52 autoantibodies in genetically susceptible individuals. We conclude that the up-regulation of Ro52 in ductal epithelium might be a triggering factor for disease progression in SS.

CD11c(+) dendritic cells rather than Langerhans cells are reduced in normal skin of immunosuppressed renal transplant recipients

The increased risk of squamous cell carcinomas (SCC) in renal transplant recipients (RTR) is related to impaired immunosurveillance as a consequence of immunosuppressive therapy. Since dendritic cells (DC) play an important role in immunosurveillance, we investigated the quantity of DC subsets and macrophages in normal skin of RTR and immunocompetent controls by immunohistochemistry. In this comparative study Langerhans' cells (LC) were present in similar numbers in RTR and controls. The number of CD11c+ DC was significantly reduced in RTR, particularly in patients on triple treatment therapy, compared with controls. Macrophages were significantly increased. Plasmacytoid DC were not detected in normal skin. The reduced quantity of CD11c+ DC and increased number of macrophages in normal skin of immunosuppressed RTR may contribute to the increased incidence of SCC in RTR. This finding underlines the role of DC subsets in immunosurveillance, and may have implications for our understanding of the effect of immunosuppression on DC subsets.

Ro52- and Ro60-specific B cell pattern in the salivary glands of patients with primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is characterized by the presence of autoantibodies against the ribonucleoprotein (RNP) particles Ro/SSA and La/SSB, and mononuclear cell infiltration of exocrine tissues, especially salivary and lachrymal glands. Low numbers of autoantigen-specific memory B cells and elevated levels of plasma cells have been detected previously in the peripheral blood (PB) of pSS patients compared to controls. As both Ro52 and Ro60-specific cells have been detected in the salivary glands (SG) of pSS patients, we aimed to characterize the SSA-specific B cell pattern in SG biopsies. A series of double immunohistochemical stainings were performed on paraffin-embedded tissue from 10 well-characterized pSS patients for each Ro52 and Ro60 along with CD19, CD5, CD20 or CD27, respectively. Ro52 and Ro60-specific cells detected in SG tissue were found to be CD19(+) B cells located outside the CD19(+)/CD20(+) B cell zones (BCZ) and also interstitially. These SSA-specific cells were also quantified. No SSA-specific cells were CD5(+), indicating that they do not belong to the B-1 B cell subset. Furthermore, no SSA-specific cells were observed within the CD20(+) BCZ. Hence, no SSA-specific memory B cells were detected in these individuals. Contrary to this, SSA-specific cells were found to be CD19(+)/CD27(++), demonstrating that they are differentiating short or long-lived plasma cells. Taken together, our findings suggest that these lower levels of SSA-specific memory B cells in PB and absence of SSA-specific memory B cells in SG of pSS patients could result from activation of these cells into plasma cells at the site of inflammation.

Low number of memory B cells in the salivary glands of patients with primary Sjögren's syndrome

We have previously shown that patients with primary Sjögren's Syndrome (pSS) show a significant reduction of autoantigen specific CD27(+) memory B cells and an abnormally elevated level of autoantibody producing plasma cells in peripheral blood (PB) compared to controls. Because both memory B cells and plasma cells have been detected in salivary glands (SG) of pSS patients, we aimed to study the B cell pattern in SG biopsies. Double immunohistochemical staining of CD20 and CD27 was carried out on paraffin-embedded SG tissue from 10 pSS patients to distinguish CD20(+)/CD27(+) memory B cells, and identify the CD20(+) glandular B cell zones (BCZ). Given that plasma blasts and plasma cells are CD27(++) and CD20(- ), additional CD138 single staining of serial sections allowed the distinction of CD27(++)/CD138(- ) plasma blasts located within the BCZ from CD27(++)/CD138(+) plasma cells that were found mostly on the periphery of the BCZ and also observed interstitially. Both BCZ and the memory B cell populations were then quantified. Contrary to what has been reported earlier through immunoflourescent staining of memory B cells in SG tissue, we have shown that there is a low number of memory B cells located within the glandular BCZ. Plasma blasts and plasma cells, however, were more abundant in the SG. Together our findings suggest that these low numbers of memory B cells in both PB and SG of pSS patients may be the result of activation of these cells into plasma cells at the site of inflammation.

Autoantigen-specific memory B cells in primary Sjögren's syndrome

Sjögren's syndrome (SS) is a systemic rheumatic autoimmune disease affecting the exocrine glandular function and is characterized by the presence of autoantibodies against the ribonucleoprotein particles, SS-A/Ro and SS-B/La, and mononuclear cell infiltration of exocrine tissues. Our aim is to characterize memory B cell pattern and function in relation to the progression of the disease, by analysing samples from a well-defined cohort of patients with primary SS. We have measured the number of Ro/La-specific plasma cells in peripheral blood mononuclear cells (PBMC) from 23 patients and 20 healthy controls by direct enzyme-linked immunospot (ELISPOT) assay. Furthermore, we quantified the Ro- and La-specific memory B cells in these individuals by a 6-day in vitro polyclonal stimulation of PBMC followed by an antigen-specific ELISPOT assay for the detection of memory B cells. In addition to this, ELISA profiling of autoantibodies was carried out using patients' plasma and supernatant, collected post-mitogen stimulation of PBMC. The average Ro60-, Ro52- and La48-specific plasma cells in PB was 9, 17 and 13 cells in 10(5) PBMC, respectively. After in vitro stimulation, these numbers increased to 43, 50 and 26 for Ro60, Ro52 and La48, correspondingly. However, the fraction of memory B cells activated into antibody-secreting cells was lower than the overall IgG B cell population. We conclude that these lower Ro/La-specific memory B cell levels may indicate that a greater portion of the Ro- and La-specific B cells are in an activated stage. This is in tune with previous reports.

Lymphotoxin-beta receptor blockade reduces CXCL13 in lacrimal glands and improves corneal integrity in the NOD model of Sjögren's syndrome

Introduction

In Sjögren's syndrome, keratoconjunctivitis sicca (dry eye) is associated with infiltration of lacrimal glands by leukocytes and consequent losses of tear-fluid production and the integrity of the ocular surface. We investigated the effect of blockade of the lymphotoxin-beta receptor (LTBR) pathway on lacrimal-gland pathology in the NOD mouse model of Sjögren's syndrome.

Methods

Male NOD mice were treated for up to ten weeks with an antagonist, LTBR-Ig, or control mouse antibody MOPC-21. Extra-orbital lacrimal glands were analyzed by immunohistochemistry for high endothelial venules (HEV), by Affymetrix gene-array analysis and real-time PCR for differential gene expression, and by ELISA for CXCL13 protein. Leukocytes from lacrimal glands were analyzed by flow-cytometry. Tear-fluid secretion-rates were measured and the integrity of the ocular surface was scored using slit-lamp microscopy and fluorescein isothiocyanate (FITC) staining. The chemokine CXCL13 was measured by ELISA in sera from Sjögren's syndrome patients (n = 27) and healthy controls (n = 30). Statistical analysis was by the two-tailed, unpaired T-test, or the Mann-Whitney-test for ocular integrity scores.

Results

LTBR blockade for eight weeks reduced B-cell accumulation (approximately 5-fold), eliminated HEV in lacrimal glands, and reduced the entry rate of lymphocytes into lacrimal glands. Affymetrix-chip analysis revealed numerous changes in mRNA expression due to LTBR blockade, including reduction of homeostatic chemokine expression. The reduction of CXCL13, CCL21, CCL19 mRNA and the HEV-associated gene GLYCAM-1 was confirmed by PCR analysis. CXCL13 protein increased with disease progression in lacrimal-gland homogenates, but after LTBR blockade for 8 weeks, CXCL13 was reduced approximately 6-fold to 8.4 pg/mg (+/- 2.7) from 51 pg/mg (+/-5.3) in lacrimal glands of 16 week old control mice. Mice given LTBR blockade exhibited an approximately two-fold greater tear-fluid secretion than control mice (P = 0.001), and had a significantly improved ocular surface integrity score (P = 0.005). The mean CXCL13 concentration in sera from Sjögren's patients (n = 27) was 170 pg/ml, compared to 92.0 pg/ml for sera from (n = 30) healthy controls (P = 0.01).

Conclusions

Blockade of LTBR pathways may have therapeutic potential for treatment of Sjögren's syndrome.

Distinct phenotypes of plasma cells in spleen and bone marrow of autoimmune NOD.B10.H2b mice

Long-lived plasma cells (PCs) residing in the bone marrow (BM) are important producers of protective antibodies. However, when reacting against self-antigens, these PCs produce autoantibodies that contribute to progression of autoimmune diseases such as Sjögren's syndrome (SS). By using a murine model of primary SS, the NOD.B10.H2b mice, we characterized phenotype and generation of PCs at different stages of the pSS disease progression. In general, the PC population found in the NOD.B10.H2b mice expressed high amounts of MHCII, IgG, and BrdU. We further demonstrate the presence of both short- and long-lived PCs in autoimmune spleen and in autoimmune BM. A long-lived PC subset was also found in the spleen and BM of non-autoimmune BALB/c mice, which have not been treated with any immunological agent. Quantitative investigation of splenic and BM PCs revealed that in the NOD.B10.H2 mice, splenic PCs migrate not only to the BM but possibly also to the sites of inflammation. Finally, BM in the aged NOD.B10.H2b mice (40-week-old) presented significantly higher quantities of long-lived PCs than BM of BALB/c mice.

Phenotypic diversity of peripheral blood plasma cells in primary Sjögren's syndrome

Production of autoantibodies is one of the main features of primary Sjögren's syndrome (pSS). Long-lived plasma cells (PC) can produce autoantibodies for prolonged period of times without being affected by immunosuppressive therapies. As of today, little is known about the long-lived PC subset and their contribution to autoimmunity. We have characterized the phenotypic and migratory properties of peripheral blood PC isolated from pSS patients (grouped by focus score, FS) and compared them to PC from rheumatoid arthritis (RA) patients and normal non-autoimmune subjects. We observed two populations of PC in all study groups, CD19+ PC and CD19- PC. Interestingly, the CD19- PC subset was most prominent in autoimmune patients (pSS and RA) compared to normal controls. Further investigation of the PC phenotype revealed that a high percentage of both CD19+ and CD19- PC isolated from pSS and RA patients did not express the CD27 marker, which is normally highly expressed on all types of PC. Differences in the expression of markers such as IgM, IgG, CD95 and CXCR3 in the group with high FS compared to FS = 1, underscore the heterogeneity of pSS patient group and demonstrate that phenotypic pattern of circulating PC associates with the severity of inflammation in the salivary glands of these patients. Our migration experiments show that addition of CXCL12 to PC in vitro, do not alter the migration potential of PC in any group tested. However, we observed an overall higher spontaneous migration of PC from pSS compared to both RA and normal controls.

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.

Levels of plasmacytoid dendritic cells and type-2 myeloid dendritic cells are reduced in peripheral blood of patients with primary Sjögren's syndrome

Objective

Sjögren's syndrome (SS) is a lymphoproliferative autoimmune disease, characterised by dryness of the mouth and eyes. Dendritic cells (DC) are potent antigen-presenting cells crucial for initiating and maintaining primary immune responses. This study quantified interferon-producing plasmacytoid DC (pDC) and two myeloid DC subsets (mDC1 and mDC2) in peripheral blood (PB) from primary SS (pSS) patients and healthy controls.

Methods

Blood samples from 31 pSS patients and 28 gender and age-matched healthy controls were analysed by flow cytometry using the Miltenyi Blood DC enumeration kit. The presence of pDC in salivary glands (SG) from pSS patients was analysed by immunohistochemistry.

Results

Patients with pSS had significantly less pDC and mDC2 in PB compared with healthy controls. Moreover, pDC are present in SG from patients with pSS.

Conclusion

Patients with pSS have alterations among DC populations in PB, and pDC are present in the SG, suggesting a potential role of these cells in SS.

Blockade of lymphotoxin-beta receptor signaling reduces aspects of Sjögren's syndrome in salivary glands of non-obese diabetic mice

Introduction

The lymphotoxin-beta receptor (LTβR) pathway is important in the development and maintenance of lymphoid structures. Blocking this pathway has proven beneficial in murine models of autoimmune diseases such as diabetes and rheumatoid arthritis. The aim of this study was to determine the effects of LTβR pathway blockade on Sjögren syndrome (SS)-like salivary gland disease in non-obese diabetic (NOD) mice.

Methods

The course of SS-like disease was followed in NOD mice that were given lymphotoxin-beta receptor-immunoglobulin fusion protein (LTβR-Ig) starting at 9 weeks of age. Treatment was given as a single weekly dose for 3, 7, or 10 weeks. Age-matched NOD mice treated with mouse monoclonal IgG1, or not treated at all, were used as controls. The severity of inflammation, cellular composition, and lymphoid neogenesis in the submandibular glands were determined by immunohistochemistry. Mandibular lymph nodes were also studied. Saliva flow rates were measured, and saliva was analyzed by a multiplex cytokine assay. The salivary glands were analyzed for CXCL13, CCL19, and CCL21 gene expression by quantitative polymerase chain reaction.

Results

Treatment with LTβR-Ig prevented the increase in size and number of focal infiltrates normally observed in this SS-like disease. Compared with the controls, the submandibular glands of LTβR-Ig-treated mice had fewer and smaller T- and B-cell zones and fewer high endothelial venules per given salivary gland area. Follicular dendritic cell networks were lost in LTβR-Ig-treated mice. CCL19 expression was also dramatically inhibited in the salivary gland infiltrates. Draining lymph nodes showed more gradual changes after LTβR-Ig treatment. Saliva flow was partially restored in mice treated with 10 LTβR-Ig weekly injections, and the saliva cytokine profile of these mice resembled that of mice in the pre-disease state.

Conclusions

Our findings show that blocking the LTβR pathway results in ablation of the lymphoid organization in the NOD salivary glands and thus an improvement in salivary gland function.

Germinal Centres in Primary Sjögren's Syndrome Indicate a Certain Clinical Immunological Phenotype

Ectopic germinal centers (GCs) can be detected in the salivary glands of approximately 1/5 of patients with Sjögren's syndrome (SS) and appear in both primary and secondary SS. Previously, ectopic GC have been associated with increased local autoantibody production. The aim of this study was to determine whether GC in primary Sjögren's syndrome (pSS) defines a distinct seroimmunological phenotype. Retrospectively, a material of 130 haematoxylin and eosin‐stained paraffin‐embedded tissue sections of minor salivary gland tissue from patients with pSS was morphologically screened for the presence of ectopic GC. GC‐like lesions were detected in 33/130 (25%) of the pSS patients. Seventy‐two pSS patients lacking these structures (GC‐) were randomly selected for comparison. Focus score was significantly increased in the GC⁺ patients compared to the GC^– patients (P = 0.035). In the GC⁺ group, 54.5% of the patients presented with anti‐Ro/SSA compared to 43.7% in the GC^– group. Anti‐La/SSB was detected in 31.3% of the GC⁺ patients compared to 25.7% of the GC^– patients. Sixty‐one percentage of GC⁺ patients presented with increased levels of IgG, a nonsignificant difference when compared to 39.4% in the GC^– patients (P = 0.089). Levels of RF, ANA, ENA, IgM and IgA were similar in both patient groups, as were ESR and CRP. In conclusion, patients with ectopic GC have a higher focus score and more often present with autoantibodies and increased levels of IgG compared to pSS patients with regular focal infiltration (GC^–). Our findings may indicate a certain seroimmunological phenotype and warrant for further prospective studies.

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.

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.

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.

Influence on Spontaneous Tissue Inflammation by the Major Histocompatibility Complex Region in the Nonobese Diabetic Mouse

We investigated the role of the major histocompatibility complex (MHC) region in the specificity of autoimmunity by analysing specifically the development of sialadenitis, but also insulitis, nephritis and autoantibody production in autoimmune-prone nonobese diabetic (NOD) mice where the MHC H2g7 haplotype had been exchanged for the H2q (NOD.Q) or H2p (NOD.P) haplotype. The exchange of H2 haplotype did not affect the frequency of sialadenitis because the H2q and H2p congenic NOD strains developed sialadenitis with the same incidence as NOD. However, the severity of sialadenitis varied among the strains, as NOD.Q >NOD >NOD.P. At 11-13 weeks of age, the NOD.Q (H2q) female mice developed more severe sialadenitis compared to NOD.P (H2p) (P=0.038). At 20 weeks, the NOD (H2g7) female mice showed more severe sialadenitis than NOD.P (P=0.049). This is in contrast to the development of insulitis in the present strains, because the incidence of insulitis was almost completely inhibited by the replacement of the H2g7 haplotype of NOD. The incidence of insulitis in NOD.Q was 11-22%, compared to 75% in NOD, which correlated well with lower titres of anti-glutamic acid decarboxylase (anti-GAD) antibodies in NOD.Q compared to NOD (P=0.009). However, the introduction of the H2q haplotype into the NOD strain instead directed the autoimmune response towards the production of lupus types of autoantibodies, because the incidence of antinuclear antibodies (ANA) in NOD.Q was 89% compared with 11% in NOD.P and 12% in NOD mice, which in turn correlated with a high incidence of nephritis in NOD.Q compared to NOD. Consequently, we show that different haplotypes of MHC are instrumental in directing the specificity of the spontaneous autoimmune inflammation.

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.

The genetic control of sialadenitis versus arthritis in a NOD.QxB10.Q F2 cross

The non-obese diabetic (NOD) mouse spontaneously develops diabetes and sialadenitis. The sialadenitis is characterized by histopathological changes in salivary glands and functional deficit similar to Sjögren's syndrome. In humans, Sjögren's syndrome could be associated with other connective tissue disorders, such as rheumatoid arthritis. In the present study the genetic control of sialadenitis in mice was compared to that of arthritis. We have previously reported a NOD locus, identified in an F2 cross with the H2(q) congenic NOD (NOD.Q) and C57BL/10.Q (B10.Q) strains, that promoted susceptibility to collagen-induced arthritis. The sialadenitis in NOD.Q showed a similar histological phenotype as in NOD, whereas no submandibular gland infiltration was found in B10.Q. The development of sialadenitis was independent of immunization with type II collagen and established arthritis. To identify the genetic control of sialadenitis, a gene segregation experiment was performed on an (NOD.QxB10.Q)F2 cross and genetic mapping of 353 F2 mice revealed one significant locus associated with sialadenitis on chromosome 4, LOD score 4.7. The NOD.Q allele-mediated susceptibility under a recessive inheritance pattern. The genetic control of sialadenitis seemed to be unique in comparison to diabetes and arthritis, as no loci associated with these diseases have been identified at the same location.

T cell proliferation and apoptosis in HIV-1-infected lymphoid tissue: impact of highly active antiretroviral therapy

T cell turnover was studied in situ in tonsillar lymphoid tissue (LT) from HIV-1-infected individuals during 48 weeks of highly active antiretroviral therapy (HAART) and compared to that of HIV-1-negative controls. Prior to therapy, CD4 cell proliferation (%CD4+ Ki67+) and apoptosis (%CD4+ TUNEL+) were increased in HIV-1-infected LT and both parameters correlated with tonsillar viral load. CD8 cell proliferation (%CD8+ Ki67+) was increased 4- to 10-fold, mainly in the germinal centers. Apoptotic CD8+ T cell levels (%CD8+ TUNEL+) were raised preferentially in the tonsillar T cell zone. The frequency of CD8+ Ki67+ and CD8+ TUNEL+ T cells correlated with tonsillar viral load and with the fraction of CD8(+) T cells expressing activation markers. During HAART, CD4 cell turnover normalized while CD8 cell turnover was dramatically reduced. However, low level viral replication concomitant with slightly elevated levels of CD8 cell turnover indicated a persistent cellular immune response in LT. In conclusion, enhanced T cell turnover may reflect effector cells related to HIV-1 infection.

Fas-induced apoptosis is a rare event in Sjögren's syndrome

The aim of this study was to perform a controlled in situ analysis on the incidence of apoptosis, investigate the expression of apoptosis-mediating proteins, and determine the frequency of apoptotic CD4+ and CD8+ T cells in Sjögren's syndrome (SS). The study was extended to patients with atrophy-fibrosis (AF) not related to SS, as well as to a control group. Immunohistochemistry and the terminal deoxynucleotidyl transferase mediated dUTP digoxigenin nick end labeling (TUNEL) method were applied to study the Fas and FasL expression and the incidence of apoptosis in salivary glands (SG) from patients with primary and secondary SS, AF, and controls. These methods were also combined to enable simultaneous detection of apoptotic and CD4+ or CD8+ T cells. Despite abundant expression of Fas and FasL in SS SG, apoptotic cells were not exceeding 1% in the foci of infiltrating mononuclear cells (IMC). Double staining showed that the frequency of apoptosis was low among both CD4+ and CD8+ T cells. Only a few TUNEL+ epithelial cells were found in all patient groups. Fas was expressed predominantly on SS IMC, single SS epithelial cells, and a few normal acinar cells, but not in AF SG. Although FasL was present on SS and AF IMC and epithelial cells, it was rarely detected in normal tissue. Consequently we demonstrate that Fas-induced apoptosis among SS SG is a rare event. Our findings support an earlier hypothesis indicating that IMC seem to be able to escape apoptosis, resulting in foci of inflammatory cells. Notably, however, no obvious correlation can be drawn to previous studies where a high incidence of apoptosis of epithelial cells was proposed as an important mechanism leading to decreased glandular function, which is a hallmark of SS.