Primary Sjögren's syndrome is characterized by distinct phenotypic and transcriptional profiles of IgD+ unswitched memory B cells

Hyperactivation and altered selection of B cells in patients with paediatric Sjogren's syndrome

OBJECTIVES

Paediatric Sjögren's syndrome (pSS) is a rare chronic autoimmune disorder, characterised by inflammation of exocrine glands. B cell hyperactivation plays a central role in adult-onset Sjogren. This study was designed to analyse B cell and T cell phenotype, levels of BAFF, and selection of autoreactive B cells in patients with pSS.

METHODS

A total of 17 patients diagnosed with pSS and 13 healthy donors (controls) comparable for age were enrolled in the study. B cell and T cell subsets and frequency of autoreactive B cells in peripheral blood were analysed by flow cytometry. Levels of BAFF were analysed by ELISA.

RESULTS

The relative frequency of total B cells, transitional, naïve and switched memory B cells was similar between pSS patients and controls. In patients with pSS, we observed a reduction in the frequency of unswitched memory B cells, an increased frequency of atypical memory B cells and an expansion of PD1hi CXCR5- T peripheral helper cells. Levels of BAFF were higher in patients with pSS compared with controls and correlated with serum levels of total IgG and titres of anti-Ro antibodies. The frequency of autoreactive B cells in the transitional, unswitched memory and plasmablast compartment was significantly higher in pSS patients than in controls.

CONCLUSIONS

Our results point to a hyperactivation of B cells in pSS. Current therapies do not seem to affect B cell abnormalities, suggesting that novel therapies targeting specifically B cell hyperactivation need to be implemented for paediatric patients.

Single-cell transcriptome profiling reveals immune and stromal cell heterogeneity in primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a complex autoimmune disease characterized by lymphocytic infiltration and exocrine dysfunction, particularly affecting the salivary gland (SG). We employed single-cell RNA sequencing to investigate cellular heterogeneity in 11 patients with pSS and 5 non-SS controls. Notably, patients with pSS exhibited downregulated SOX9 in myoepithelial cells, potentially associated with impaired epithelial regeneration. An expanded ACKR1+ endothelial subpopulation in patients with pSS suggested a role in facilitating lymphocyte transendothelial migration. Our analysis of immune cells revealed expanded IGHD+ naive B cells in peripheral blood from patients with pSS. Pseudotime trajectory analysis outlined a bifurcated differentiation pathway for peripheral B cells, enriching three subtypes (VPREB3+ B, BANK1+ B, CD83+ B cells) within SGs in patients with pSS. Fibroblasts emerged as pivotal components in a stromal-immune interaction network, potentially driving extracellular matrix disruption, epithelial regeneration impairment, and inflammation. Our study illuminates immune and stromal cell heterogeneity in patients with pSS, offering insights into therapeutic strategies.

Exploring Perturbations in Peripheral B Cell Memory Subpopulations Early after Kidney Transplantation Using Unsupervised Machine Learning

BACKGROUND

B cells have a significant role in transplantation. We examined the distribution of memory subpopulations (MBCs) and naïve B cell (NBCs) phenotypes in patients soon after kidney transplantation. Unsupervised machine learning cluster analysis is used to determine the association between the cellular phenotypes and renal function.

METHODS

MBC subpopulations and NBCs from 47 stable renal transplant recipients were characterized by flow cytometry just before (T0) and 6 months after (T6) transplantation. T0 and T6 measurements were compared, and clusters of patients with similar cellular phenotypic profiles at T6 were identified. Two clusters, clusters 1 and 2, were formed, and the glomerular filtration rate was estimated (eGFR) for these clusters.

RESULTS

A significant increase in NBC frequency was observed between T0 and T6, with no statistically significant differences in the MBC subpopulations. Cluster 1 was characterized by a predominance of the NBC phenotype with a lower frequency of MBCs, whereas cluster 2 was characterized by a high frequency of MBCs and a lower frequency of NBCs. With regard to eGFR, cluster 1 showed a higher value compared to cluster 2.

CONCLUSIONS

Transplanted kidney patients can be stratified into clusters based on the combination of heterogeneity of MBC phenotype, NBCs and eGFR using unsupervised machine learning.

Added value of lymphocyte subpopulations in the classification of Sjögren's syndrome

Sjögren's Syndrome (SjS) is a chronic systemic immune-mediated inflammatory disease characterized by lymphocytic infiltration and consequent lesion of exocrine glands. SjS diagnosis and classification remains a challenge, especially at SjS onset, when patients may have milder phenotypes of the disease or uncommon presentations. New biomarkers are needed for the classification of SjS, thus, we aimed to evaluate the added-value of lymphocyte subpopulations in discriminating SjS and non-Sjögren Sicca patients. Lymphocyte subsets from 62 SjS and 63 Sicca patients were characterized by flow cytometry. The 2002 AECG and the 2016 ACR/EULAR SjS classification criteria were compared with clinical diagnosis. The added discriminative ability of joining lymphocytic populations to classification criteria was assessed by the area under the Receiver-Operating-Characteristic Curve (AUC). Considering clinical diagnosis as the gold-standard, we obtained an AUC = 0.952 (95% CI: 0.916-0.989) for AECG and an AUC = 0.921 (95% CI: 0.875-0.966) for ACR/EULAR criteria. Adding Tfh and Bm1 subsets to AECG criteria, performance increased, attaining an AUC = 0.985 (95% CI: 0.968-1.000) (p = 0.021). Th1/Breg-like CD24^hiCD27⁺ and switched-memory B-cells maximized the AUC of ACR/EULAR criteria to 0.953 (95% CI: 0.916-0.990) (p = 0.043). Our exploratory study supports the potential use of lymphocyte subpopulations, such as unswitched memory B cells, to improve the performance of classification criteria, since their discriminative ability increases when specific subsets are added to the criteria.

Emerging of a new CD3+CD31HCD184+ tang cell phenothype in Sjögren’s syndrome induced by microencapsulated human umbilical cord matrix-derived multipotent stromal cells

Background

Sjögren’s syndrome (SS) is an autoimmune disease hallmarked by infiltration and destruction of exocrine glands. Currently, there is no therapy that warrants full recovery of the affected tissues. Umbilical cord-derived multipotent stromal cells, microincapsulated in an endotoxin-free alginate gel (CpS-hUCMS), were shown to modulate the inflammatory activity of PBMCs in SS patients in vitro, through release of soluble factors (TGFβ1, IDO1, IL6, PGE2, VEGF). These observations led us to set up the present study, aimed at defining the in vitro effects of CpS-hUCMS on pro- and anti-inflammatory lymphocyte subsets involved in the pathogenesis of SS.

Methods and results

Peripheral blood mononuclear cells (PBMCs) upon collection from SS patients and matched healthy donors, were placed in co-culture with CpS-hUCMS for five days. Cellular proliferation and T- (Tang, Treg) and B- (Breg, CD19+) lymphocyte subsets were studied by flow cytometry, while Multiplex, Real-Time PCR, and Western Blotting techniques were employed for the analysis of transcriptome and secretome. IFNγ pre-treated hUCMS were assessed with a viability assay and Western Blotting analysis before co-culture. After five days co-culture, CpS-hUCMS induced multiple effects on PBMCs, with special regard to decrease of lymphocyte proliferation, increase of regulatory B cells and induction of an angiogenic T cell population with high expression of the surface marker CD31, that had never been described before in the literature.

Conclusion

We preliminarily showed that CpS-hUCMS can influence multiple pro- and anti-inflammatory pathways that are deranged in SS. In particular, Breg raised and a new Tang phenothype CD3+CD31HCD184+ emerged. These results may considerably expand our knowledge on multipotent stromal cell properties and may open new therapeutic avenues for the management of this disease, by designing ad hoc clinical studies.

Human B-cell subset identification and changes in inflammatory diseases

Our understanding of the B-cell subsets found in human blood and their functional significance has advanced greatly in the past decade. This has been aided by the evolution of high dimensional phenotypic tools such as mass cytometry and single-cell RNA sequencing which have revealed heterogeneity in populations that were previously considered homogenous. Despite this, there is still uncertainty and variation between studies as to how B-cell subsets are identified and named. This review will focus on the most commonly encountered subsets of B cells in human blood and will describe gating strategies for their identification by flow and mass cytometry. Important changes to population frequencies and function in common inflammatory and autoimmune diseases will also be described.

Altered B cell phenotype and CD27+ memory B cells are associated with clinical features and environmental exposure in Colombian systemic lupus erythematosus patients

Background

B lymphocytes are dysregulated in Systemic Lupus Erythematosus (SLE) including the expansion of extrafollicular B cells in patients with SLE of African American ancestry, which is associated with disease activity and nephritis. The population of Colombia has a mixture of European, Native American, and African ancestry. It is not known if Colombian patients have the same B cell distributions described previously and if they are associated with disease activity, clinical manifestations, and environmental exposures.

Objective

To characterize B cell phenotype in a group of Colombian Systemic Lupus Erythematosus patients with mixed ancestry and determine possible associations with disease activity, clinical manifestations, the DNA methylation status of the IFI44L gene and environmental exposures.

Materials and methods

Forty SLE patients and 17 healthy controls were recruited. Cryopreserved peripheral B lymphocytes were analyzed by multiparameter flow cytometry, and the DNA methylation status of the gene IFI44L was evaluated in resting Naive B cells (rNAV).

Results

Extrafollicular active Naive (aNAV) and Double Negative type 2, DN2 (CD27− IgD− CD21− CD11c+) B cells were expanded in severe active patients and were associated with nephritis. Patients had hypomethylation of the IFI44L gene in rNAV cells. Regarding environmental exposure, patients occupationally exposed to organic solvents had increased memory CD27+ cells (SWM).

Conclusion

aNAV and DN2 extrafollicular cells showed significant clinical associations in Colombian SLE patients, suggesting a relevant role in the disease’s pathophysiology. Hypomethylation of the IFI44L gene in resting Naive B cells suggests that epigenetic changes are established at exceedingly early stages of B cell ontogeny. Also, an alteration in SWM memory cells was observed for the first time in patients exposed to organic solvents. This opens different clinical and basic research possibilities to corroborate these findings and deepen the knowledge of the relationship between environmental exposure and SLE.

Decreased BAFF Receptor Expression and Unaltered B Cell Receptor Signaling in Circulating B Cells from Primary Sjögren's Syndrome Patients at Diagnosis

Animal models of autoimmunity and human genetic association studies indicate that the dysregulation of B-cell receptor (BCR) signaling is an important driver of autoimmunity. We previously showed that in circulating B cells from primary Sjögren’s syndrome (pSS) patients with high systemic disease activity, protein expression of the BCR signaling molecule Bruton’s tyrosine kinase (BTK) was increased and correlated with T-cell infiltration in the target organ. We hypothesized that these alterations could be driven by increased B-cell activating factor (BAFF) levels in pSS. Here, we investigated whether altered BCR signaling was already present at diagnosis and distinguished pSS from non-SS sicca patients. Using (phospho-)flow cytometry, we quantified the phosphorylation of BCR signaling molecules, and investigated BTK and BAFF receptor (BAFFR) expression in circulating B cell subsets in an inception cohort of non-SS sicca and pSS patients, as well as healthy controls (HCs). We found that both BTK protein levels and BCR signaling activity were comparable among groups. Interestingly, BAFFR expression was significantly downregulated in pSS, but not in non-SS sicca patients, compared with HCs, and correlated with pSS-associated alterations in B cell subsets. These data indicate reduced BAFFR expression as a possible sign of early B cell involvement and a diagnostic marker for pSS.

Immunoregulatory effects of dental mesenchymal stem cells on T and B lymphocyte responses in primary Sjögren's syndrome

Background: In this article, the authors investigate the modulatory effects of dental mesenchymal stem cells (MSCs) on lymphocyte responses in primary Sjögren's syndrome (pSS), which is an autoimmune disease resulting from keratoconjunctivitis sicca and xerostomia. Methods: Mononuclear cells isolated from pSS patients cultured with or without dental MSCs and analyzed for lymphocyte responses via flow cytometry. Results: Dental-follicle (DF)- and dental-pulp (DP)-MSCs downregulated CD4⁺ T lymphocyte proliferation by increasing Fas-ligand expression on T lymphocytes and FoxP3 expressing Tregs, and decreasing intracellular IFN-γ and IL-17 secretion in pSS patients. DF-MSCs decreased the plasma B cell ratio in the favor of naive B cell population in pSS patients' mononuclear cells. Conclusion: DF- and DP-MSCs can be the new cellular therapeutic candidates for the regulation of immune responses in pSS.

Corneal sub-basal nerve plexus assessment and its association with phenotypic features and lymphocyte subsets in Sjögren's Syndrome

PURPOSE

To assess and compare corneal sub-basal nerve plexus morphology with circulating lymphocyte subsets, immunologic status and disease activity in Sjögren syndrome (SjS) patients.

METHODS

Fifty-five SjS patients, 63 Sicca patients (not fulfilling SjS criteria), 18 rheumatoid arthritis (RA) patients and 20 healthy controls (HC) were included. Systemic disease activity in SjS was assessed with the ESSDAI score. Lymphocyte subpopulations were studied with flow cytometry. Corneal confocal microscopy and ImageJ software were used to characterize corneal sub-basal nerve plexus in terms of nerve density (CNFD), length (CNFL) and tortuosity (CNFT). Conventional dry eye tests were also performed.

RESULTS

CNFL and CNFD were lower in SjS, Sicca and RA groups, compared to HC (p < 0.001 for both SjS and Sicca); CNFL p = 0.005, CNFD p = 0.018 in RA). CNFT was higher in SjS, followed by Sicca, RA and HC. A negative correlation was found between ESSDAI score and CNFL (r=-0.735, p = 0.012). CNFL correlated negatively with IL21⁺ CD8⁺ T cells (r=-0.279, p = 0.039) and a positively with total memory (r = 0.299, p = 0.027), unswitched memory (r = 0.281, p = 0.038) and CD24^Hi CD27⁺ (r = 0.278, p = 0.040) B cells. CNFD showed a tendency to significance in its negative correlation with ESSDAI (r=-0.592, p = 0.071) and in its positive correlation with switched memory B cells (r = 0.644, p = 0.068).

CONCLUSIONS

This is the first study aiming to correlate ocular findings with lymphocyte subsets in SjS. The associations founded between CNFL and CNFD and disease activity, IL21⁺ follicular T cells and some B-cell subsets suggest that corneal nerve damage may parallel systemic disease activity and inflammatory cells' dynamics.

Peripheral B-Cell Immunophenotyping Identifies Heterogeneity in IgG4-Related Disease

Objectives

To elucidate heterogeneity of IgG4-related disease (IgG4-RD) based on B cell immunophenotyping.

Methods

Immunophenotyping of 4 B-cell subsets in peripheral blood from patients with active IgG4-RD (aIgG4-RD, n=105) was performed using flow cytometry to get preliminary B-cell heterogeneity spectrum. Then 10 B-cell subsets were characterized in aIgG4-RD (n = 49), remissive IgG4-RD (rIgG4-RD, n = 49), and healthy controls (HCs, n = 47), followed by principal components analysis (PCA) and cluster analysis to distinguish B-cell immunophenotypes and classify IgG4-RD patients into subgroups.

Results

Cluster analysis identified two endotypes in 105 aIgG4-RD patients based on 4 B-cell subsets: Group1 with higher Breg and naive B cells (n = 48), and Group2 with higher plasmablasts and memory B cells (MBCs) (n = 57). PCA indicated that aIgG4-RD consisted of plasmablast-naive B cell and MBCs-Breg axes abnormalities. There was a negative relationship between naive B cells and disease activity. Both plasmablasts and MBCs were positively associated with serological biomarkers. Cluster analysis stratified aIgG4-RD patients into 3 subgroups based on 10 B-cell subsets: subgroup1 with low MBCs and normal Breg, subgroup2 with high MBCs and low Breg, and subgroup3 with high plasmablasts and low naive B cells. Patients in subroup2 and subgroup3 were more likely to be resistant to treatment.

Conclusion

Patients with aIgG4-RD can be divided into 3 subgroups based on B cell heterogeneity. The B cell immunophenotyping could help elucidate the pathogenesis of IgG4-RD, identify patients with potential refractory IgG4-RD, and provide important information for the development of new therapies.

B cell subset composition segments clinically and serologically distinct groups in chronic cutaneous lupus erythematosus

OBJECTIVE

While the contribution of B-cells to SLE is well established, its role in chronic cutaneous lupus erythematosus (CCLE) remains unclear. Here, we compare B-cell and serum auto-antibody profiles between patients with systemic lupus erythematosus (SLE), CCLE, and overlap conditions.

METHODS

B-cells were compared by flow cytometry amongst healthy controls, CCLE without systemic lupus (CCLE+/SLE-) and SLE patients with (SLE+/CCLE+) or without CCLE (SLE+/CCLE-). Serum was analyed for autoreactive 9G4+, anti-double-stranded DNA, anti-chromatin and anti-RNA antibodies by ELISA and for anti-RNA binding proteins (RBP) by luciferase immunoprecipitation.

RESULTS

Patients with CCLE+/SLE- share B-cell abnormalities with SLE including decreased unswitched memory and increased effector B-cells albeit at a lower level than SLE patients. Similarly, both SLE and CCLE+/SLE- patients have elevated 9G4+ IgG autoantibodies despite lower levels of anti-nucleic acid and anti-RBP antibodies in CCLE+/SLE-. CCLE+/SLE- patients could be stratified into those with SLE-like B-cell profiles and a separate group with normal B-cell profiles. The former group was more serologically active and more likely to have disseminated skin lesions.

CONCLUSION

CCLE displays perturbations in B-cell homeostasis and partial B-cell tolerance breakdown. Our study demonstrates that this entity is immunologically heterogeneous and includes a disease segment whose B-cell compartment resembles SLE and is clinically associated with enhanced serological activity and more extensive skin disease. This picture suggests that SLE-like B-cell changes in primary CCLE may help identify patients at risk for subsequent development of SLE. B-cell profiling in CCLE might also indentify candidates who would benefit from B-cell targeted therapies.

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

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

A Proinflammatory Cytokine Network Profile in Th1/Type 1 Effector B Cells Delineates a Common Group of Patients in Four Systemic Autoimmune Diseases

OBJECTIVE

The effector T cell and B cell cytokine networks have been implicated in the pathogenesis of systemic autoimmune diseases, but the association of these cytokine networks with the heterogeneity of clinical manifestations and immune profiles has not been carefully examined. This study was undertaken to examine whether cytokine profiles can delineate distinct groups of patients in 4 systemic autoimmune diseases (systemic lupus erythematosus, Sjögren's syndrome, rheumatoid arthritis, and systemic sclerosis).

METHODS

A total of 179 patients and 48 healthy volunteers were enrolled in the multicenter cross-sectional PRECISE Systemic Autoimmune Diseases (PRECISESADS) study. Multi-low-dimensional omics data (cytokines, autoantibodies, circulating immune cells) were examined. Coculture experiments were performed to test the impact of the cytokine microenvironment on T cell/B cell cross-talk.

RESULTS

A proinflammatory cytokine profile defined by high levels of CXCL10, interleukin-6 (IL-6), IL-2, and tumor necrosis factor characterized a distinct group of patients in the 4 systemic autoimmune diseases. In each disease, this proinflammatory cluster was associated with a specific circulating immune cell signature, more severe disease, and higher levels of autoantibodies, suggesting an uncontrolled proinflammatory Th1 immune response. We observed in vitro that B cells reinforce Th1 differentiation and naive T cell proliferation, leading to the induction of type 1 effector B cells and IgG production. This process was associated with an increase in CXCL10, IL-6, IL-2, and interferon-γ production.

CONCLUSION

This composite analysis brings new insights into human B cell functional heterogeneity based on T cell/B cell cross-talk, and proposes a better stratification of patients with systemic autoimmune diseases, suggesting that combined biomarkers would be of great value for the design of personalized treatments.

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

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

Autoimmune B Cell Repertoire in a Mouse Model of Sjögren's Syndrome

In genetically prone individuals, chronic immune activation may lead to expansion of autoreactive lymphocyte clones that can induce organ damage developing autoimmune disorders. Sjögren’s Syndrome (SjS) is a systemic chronic autoimmune disease that primarily affects exocrine glands. Despite the accumulated evidences of profound B-cell alterations of humoral immunity, the repertoire and development of B-cell autoreactivity in SjS remains to be determined. We hypothesize that SjS mice will have an increased frequency of self-reactive B cells with a progressive evolution to antigen-driven oligoclonality. Here, we study the B cell repertoire of NOD.H-2^h4 mice, a mouse model of spontaneous autoimmunity mimicking SjS without developing diabetes. A library of 168 hybridomas from NOD.H-2^h4 mice and 186 C57BL/6J splenocytes at different ages was created. The presence of mono or polyreactive autoantibodies to several antigens was evaluated by ELISA, and their staining patterns and cellular reactivity were tested by IFA and FACS. We observed a higher frequency of autoreactivity among B-cell clones from NOD.H-2^h4 mice as compared to wild-type mice. The presence of polyreactive and autoreactive IgG clones increased with mice age. Strikingly, all anti-Ro52 autoantibodies were polyreactive. No loss of polyreactivity was observed upon antibody class switching to IgG. There was a progression to oligoclonality in IgG B cells with mice aging. Our results indicate that in the NOD.H-2^h4 mouse model of SjS, IgG+ B cells are mainly polyreactive and might expand following an unknown antigen-driven positive selection process.

Human marginal zone B cell development from early T2 progenitors

B cells emerge from the bone marrow as transitional (TS) B cells that differentiate through T1, T2, and T3 stages to become naive B cells. We have identified a bifurcation of human B cell maturation from the T1 stage forming IgMhi and IgMlo developmental trajectories. IgMhi T2 cells have higher expression of α4β7 integrin and lower expression of IL-4 receptor (IL4R) compared with the IgMlo branch and are selectively recruited into gut-associated lymphoid tissue. IgMhi T2 cells also share transcriptomic features with marginal zone B cells (MZBs). Lineage progression from T1 cells to MZBs via an IgMhi trajectory is identified by pseudotime analysis of scRNA-sequencing data. Reduced frequency of IgMhi gut-homing T2 cells is observed in severe SLE and is associated with reduction of MZBs and their putative IgMhi precursors. The collapse of the gut-associated MZB maturational axis in severe SLE affirms its existence in health.

Utility of lymphocyte phenotype profile to differentiate primary Sjögren syndrome from Sicca syndrome

BACKGROUND

blood B cell profile has been proposed to have diagnostic utility in primary Sjögren syndrome (pSS), but the potential utility of advanced lymphocyte profiling to differentiate between pSS and Sicca syndrome has not been fully investigated.

METHODS

distribution of peripheral lymphocyte subpopulations was analysed by flow cytometry in 68 patients with pSS, 26 patients with Sicca syndrome and 23 healthy controls. The ability to discriminate between pSS and Sicca syndrome was analysed using the area under the curve (AUC) of the receiver operating characteristic curve of the different lymphocyte subsets.

RESULTS

the ratio between naïve/memory B cell proportions showed an AUC of 0.742 to differentiate pSS and Sicca syndrome, with a sensitivity of 76.6% and a specificity of 72% for a cut-off value of 3.4. The ratio of non-switched memory B cells to activated CD4+ T cells percentage (BNSM/CD4ACT) presented the highest AUC (0.840) with a sensitivity of 83.3% and specificity of 81.7% for a cut-off value < 4.1. To differentiate seronegative pSS patients from Sicca patients the BNSM/CD4ACT ratio exhibited an AUC of 0.742 (sensitivity 75%, specificity 66.7%, cut-off value < 4.4), and the number of naïve CD4 T cells had an AUC of 0.821 (sensitivity 76.9%, specificity 88.9%, cut-off value < 312/mm3).

CONCLUSION

patients with pSS show a profound imbalance in the distribution of circulating T and B lymphocytes subsets. The ratio BNSM/CD4ACT is useful to discriminate between pSS and Sicca syndrome.

Innate Immunity and Biological Therapies for the Treatment of Sjögren's Syndrome

Sjögren's syndrome (SS) is a systemic autoimmune disorder affecting approximately 3% of the population in the United States. This disease has a female predilection and affects exocrine glands, including lacrimal and salivary glands. Dry eyes and dry mouths are the most common symptoms due to the loss of salivary and lacrimal gland function. Symptoms become more severe in secondary SS, where SS is present along with other autoimmune diseases like systemic lupus erythematosus, systemic sclerosis, or rheumatoid arthritis. It is known that aberrant activation of immune cells plays an important role in disease progression, however, the mechanism for these pathological changes in the immune system remains largely unknown. This review highlights the role of different immune cells in disease development, therapeutic treatments, and future strategies that are available to target various immune cells to cure the disease.

The presence of anti-nuclear antibodies alone is associated with changes in B cell activation and T follicular helper cells similar to those in systemic autoimmune rheumatic disease

BACKGROUND

Diagnosis of systemic autoimmune rheumatic diseases (SARD) relies on the presence of hallmark anti-nuclear antibodies (ANA), many of which can be detected years before clinical manifestations. However, ANAs are also seen in healthy individuals, most of whom will not develop SARD. Here, we examined a unique cohort of asymptomatic ANA⁺ individuals to determine whether they share any of the cellular immunologic features seen in SARD.

METHODS

Healthy ANA^- controls and ANA⁺ (ANA ≥1:160 by immunofluorescence) participants with no SARD criteria, with at least one criterion (undifferentiated connective tissue disease (UCTD)), or meeting SARD classification criteria were recruited. Peripheral blood cellular immunological changes were assessed by flow cytometry and transcript levels of BAFF, interferon (IFN)-induced and plasma cell-expressed genes were quantified by NanoString.

RESULTS

A number of the immunologic abnormalities seen in SARD, including changes in peripheral B (switched memory) and T (iNKT, T regulatory, activated memory T follicular helper) subsets and B cell activation, were also seen in asymptomatic ANA⁺ subjects and those with UCTD. The extent of these immunologic changes correlated with ANA titer or the number of different specific ANAs produced. Principal component analysis of the cellular data indicated that a significant proportion of asymptomatic ANA⁺ subjects and subjects with UCTD clustered  with patients with early SARD, rather than ANA^- healthy controls.

CONCLUSIONS

ANA production is associated with altered T and B cell activation even in asymptomatic individuals. Some of the currently accepted cellular features of SARD may be associated with ANA production rather than the immunologic events that cause symptoms in SARD.

Clinical Efficacy and Safety of Baminercept, a Lymphotoxin β Receptor Fusion Protein, in Primary Sjögren's Syndrome: Results From a Phase II Randomized, Double-Blind, Placebo-Controlled Trial

OBJECTIVE

To evaluate the clinical efficacy and safety of baminercept, a lymphotoxin β receptor IgG fusion protein (LTβR-Ig), for the treatment of primary Sjögren's syndrome (SS), and to explore the possible mechanisms of action of this treatment.

METHODS

In this multicenter trial, 52 patients with primary SS were randomized in a 2:1 ratio to receive subcutaneous injections of 100 mg of baminercept every week for 24 weeks or matching placebo. The primary end point was the change between screening and week 24 in the stimulated whole salivary flow (SWSF) rate. Secondary end points included the European League Against Rheumatism Sjögren's Syndrome Disease Activity Index (ESSDAI), as well as measurements of select chemokines and cytokines and enumeration of peripheral blood B and T cell subsets.

RESULTS

The change from baseline to week 24 in the SWSF rate was not significantly different between the baminercept and placebo treatment groups (baseline-adjusted mean change -0.01 versus 0.07 ml/minute; P = 0.332). The change in the ESSDAI during treatment was also not significantly different between the treatment groups (baseline-adjusted mean change -1.23 versus -0.15; P = 0.104). Although the incidence of adverse events was similar between the treatment groups, baminercept therapy was associated with a higher incidence of liver toxicity, including 2 serious adverse events. Baminercept also produced a significant decrease in plasma levels of CXCL13 and significant changes in the number of circulating B and T cells, consistent with its known inhibitory effects on LTβR signaling.

CONCLUSION

In this trial, treatment with baminercept failed to significantly improve glandular and extraglandular disease in patients with primary SS, despite evidence from mechanistic studies showing that it blocks LTβR signaling.

Could Lymphocyte Profiling be Useful to Diagnose Systemic Autoimmune Diseases?

Considering the implications of B, T, and natural killer (NK) cells in the pathophysiology of systemic autoimmune diseases, the assessment of their distribution in the blood could be helpful for physicians in the complex process of determining a precise diagnosis. In primary Sjögren's syndrome, transitional and active naive B cells are increased and memory B cells are decreased compared to healthy controls and other systemic diseases. However, their utility to improve the accuracy of classification criteria has not been proven. In early untreated rheumatoid arthritis, proportions of regulatory T cells are constantly reduced, but other patterns are difficult to determine given the heterogeneity of published studies. In systemic lupus erythematosus, the lack of studies using large cohorts of patients and the diversity of the possible pathological mechanisms involved are also important impediments. Nevertheless, transitional B cell and plasma cell proportions are increased in most of the studies, the CD4/CD8 ratio is decreased, and the number of NK cells is reduced. Despite the low number of studies, anomalies of lymphocyte subset distribution was also described in ANCA-associated vasculitis, systemic scleroderma, and myositis. For now, flow cytometric analysis of lymphocyte subsets has focused mainly on specific subpopulations and is more useful for basic and translational research than for diagnostics in clinical practice. However, new modern methods such as mass cytometry and bioinformatics analyses may offer the possibility to simultaneously account for the relative proportions of multiple lymphocyte subsets and define a global profile in homogeneous groups of patients. The years to come will certainly incorporate such global lymphocyte profiling in reclassification of systemic autoimmune diseases.

Association between memory B-cells and clinical and immunological features of primary Sjögren's syndrome and Sicca patients

B-cells play a pivotal role in primary Sjögren's syndrome (pSS) pathogenesis. We aim to (1) evaluate the distribution of B-lymphocyte subpopulations in pSS and Sicca patients, (2) establish cut-off points that discriminate pSS from controls, (3) evaluate the association between memory B-cells and phenotypic features in pSS. We included 57 pSS patients, 68 Sicca and 24 healthy controls. Circulating B-cells were characterized by flow cytometry as naïve and memory subsets and classified from Bm1 to Bm5. Compared to controls, pSS patients had lower percentages (29.5 vs 44.4%) and absolute numbers (47 vs 106 cells/µl) of memory B-cells. Through ROC curves, a cut-off of ≤ 58 total memory B-cells/µl yielded a specificity of 0.88 and a sensitivity of 0.60 for pSS, and was met by 59.6% of pSS patients, 38.8% of Sicca and 12.5% of controls. A cut-off of < 23.5 Switched-memory B-cells/µl yielded a specificity of 0.88 and a sensitivity of 0.54 and was met by 54.4% of pSS patients, 37.3% of Sicca and 12.5% of controls. In pSS, lower total memory B-cells count was associated with longer disease duration (14.3 vs 8.1 years, p = 0.006) and more active disease profile, as evaluated by the European League Against Rheumatism (EULAR) Sjögren's Syndrome Disease Activity Index (ESSDAI) (3.1 vs 1.4, p = 0.043). Decreased numbers of memory B-cells clearly discriminated pSS from controls and can also have prognostic value. It remains to be clarified whether Sicca patients with decreased memory B-cells represent pSS and if B-cell profiling could help in the diagnosis of pSS.

B cells in the pathogenesis of primary Sjögren syndrome

Primary Sjögren syndrome (pSS) is a prototypical autoimmune disease. The involvement of B cells in the pathogenesis of pSS has long been suspected on the basis of clinical observations that include the presence of serum autoantibodies, hypergammaglobulinaemia, increased levels of free light chains and increased risk of B cell lymphoma. Moreover, the composition of the B cell subset is altered in pSS. In this Review, we discuss the mechanisms that support the increased activation of B cells in pSS, including genetic and epigenetic factors and environmental triggers that promote B cell activation via the innate immune system. B cell activating factor (BAFF, also known as TNF ligand superfamily member 13B) is at the crossroads of this process. An important role also exists for the target tissue (exocrine glands, namely the salivary and lachrymal glands), which promotes local B cell activation. This continuous stimulation of B cells is the main driver of lymphomatous escape. Identification of the multiple steps that support B cell activation has led to the development of promising targeted therapies that will hopefully lead to the development of an efficient therapeutic strategy for pSS.

Altered B lymphocyte homeostasis and functions in systemic sclerosis

Beyond the production of autoantibodies, B-cells are thought to play a role in systemic sclerosis (SSc) by secreting proinflammatory/profibrotic cytokines. B-cells are a heterogeneous population with different subsets distinguished by their phenotypes and cytokine production. Data about B-cell subsets, cytokine production and intracellular pathways leading to this production are scarce in SSc. The aim of our study was to describe B-cell homeostasis, activation, proliferation, cytokine production in B-cells and serum and B-cell intracellular signaling pathways in SSc. We hypothezided that B-cell homeostasis and cytokine production were altered in SSc and could be explained by serum cytokine as well as by intracellular signaling pathway abnormalities. Forty SSc patients and 20 healthy controls (HC) were prospectively included. B-cell subsets were determined by flow cytometry using CD19, CD21, CD24, CD38, CD27, IgM and IgD. CD25, CD80, CD95, HLA-DR were used to assess B-cell activation. Intracellular production of IL-10 and IL-6 were assessed by flow cytometry after TLR9 and CD40 stimulation. IL-6, IL-10, Ki67, Bcl2 mRNA were quantified in B-cells. Cytokine production was also assessed in sera and supernatants of B-cell culture, using a multiplex approach. Signaling pathways were studied through phosphorylation of mTOR, ERK, STAT3, STAT5 using a flow cytometry approach. We found that SSc patients exhibited an altered peripheral blood B-cell subset distribution, with decreased memory B-cells but increased proportion of naive and CD21^LoCD38^Lo B-cell subsets. We observed an increased expression of activation markers (CD80, CD95, HLA-DR) on some B-cell subsets, mainly the memory B-cells. Secretion of IL-6, BAFF and CXCL13 were increased in SSc sera. There was no correlation between the peripheral blood B-cell subsets and the serum concentrations of these cytokines. After stimulation, we observed a lower proportion of IL-10 and IL-6 producing B-cells in SSc. Finally, we observed a significant decrease of mTOR phosphorylation in SSc patient B-cells. In conclusion, we observed an altered B-cell homeostasis in SSc patients compared to HC. Memory B-cells were both decreased and activated in patients. IL-10 producing B-cells were decreased in SSc. This decrease was associated with an alteration of mTOR phosphorylation in B-cells. Conversely, there was no correlation between serum cytokine profile and B-cell homeostasis alterations.

Bilateral striopallidodentate calcinosis associated with Sjögren's syndrome and IgDλ monoclonal gammopathy of undetermined significance

We presented the first case of bilateral striopallidodentate calcinosis secondary to Sjögren's syndrome. Further consideration should be given to the association between Sjögren's syndrome and bilateral striopallidodentate calcinosis, because Sjögren's syndrome is latent, but more frequent than other autoimmune diseases.

Insight into pathogenesis of Sjögren's syndrome: Dissection on autoimmune infiltrates and epithelial cells

Sjögren's syndrome (SS) is a chronic autoimmune disease with broad clinical spectrum, extending from benign exocrinopathy to severe systemic disease and lymphoma development. The glandular and extraglandular dysfunction of SS is associated with lymphocytic infiltrates that invade the epithelial structures of affected organs. The in-depth study of autoimmune lesions in the minor salivary glands (MSG), which are the major target-organ of SS responses, revealed that the lymphocytic infiltrates vary in severity and composition among SS-patients, are full-blown at diagnosis and remain unchanged thereafter. Although the pathogenetic pathways underlying SS have not yet elucidated, it is well-established that glandular epithelial cells are central regulators of local autoimmune responses. Moreover, chronic inflammation affects epithelial function and phenotype, which strengthens or weakens their immunoregulatory/secretory function, leading to deterioration of autoimmune phenomena. Herein, the current findings regarding the autoimmune lesions, the role of epithelial cells and their interaction with infiltrating lymphocytic cells are discussed.

Multiple Roles for B-Lymphocytes in Sjogren's Syndrome

Sjogren’s syndrome (SS) is a complex heterogeneous autoimmune disease resulting in loss of salivary gland and lacrimal gland function that may include multiple systemic manifestations including lymphoma. Multiple cell types participate in disease pathogenesis. This review discusses evidence for abnormal B cell subpopulations in patients with SS, critical roles of B cells in SS and the status of B cell–directed therapies in the management of patients with SS.

Exploring BAFF: its expression, receptors and contribution to the immunopathogenesis of Sjögren's syndrome

SS is an autoimmune condition characterized by exocrine gland destruction, autoantibody production, immune complex deposition and systemic complications associated with lymphocytic infiltration of many organs. Genetic, environmental and viral factors play a role in disease aetiology, however, the exact mechanisms driving the immunopathogenesis of SS remain uncertain. Here we discuss a role for B cell activating factor (BAFF), whereby B cell hyperactivity and increased BAFF secretion observed in patients and animal models of the disease can be explained by the altered expression of cell-specific BAFF/BAFF receptor (BAFF-R) variants in several immune cell types. Understanding the role of BAFF/BAFF-R heterogeneity in SS pathogenesis could help to facilitate new treatment strategies for patients.

Clinical and immunological consequences of total glucosides of paeony treatment in Sjögren's syndrome: A randomized controlled pilot trial

BACKGROUND

The total glucosides of paeony (TGP) can inhibit inflammation and alleviate symptoms in autoimmune diseases. This study investigated the clinical and immunological consequences of TGP treatment in patients with primary Sjögren's syndrome (SS).

METHODS

We conducted a randomized, double-blinded, placebo-controlled clinical trial in 45 patients with primary SS. Patients were randomized at 2:1 ratio to either TGP group (n=29) or placebo group (n=16) and followed up for 24weeks. The primary outocme was the European League Against Rheumatism Sjögren's Syndrome Patient Reported Index (ESSPRI). The secondary outcomes were stimulated and unstimulated salivary flow rate, Schirmer's test and erythrocyte sedimentation rate (ESR), immuneglobulin (Ig), anti-nuclear antibody (ANA), anti-SSA, and anti-SSB. The proportions of B cells in peripheral blood and the levels of serum inerleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ) and B cell activating factor belonging to the TNF family (BAFF) were measured at baseline and at the end of follow up of 24weeks.

RESULTS

The average score of ESSPRI in both groups had no statistical significance at 24th week. The mean of ESSPRI in the dry-mouth part of questionnaire in patients who scored 3 to 6 points was significantly reduced in the TGP group changed from (4.81±0.60) at baseline to (4.20±1.46) (P=0.027) at week 24. Stimulated salivary flow rate increased at week 24 from (1.80±0.39) to (2.01±0.51) (P=0.031) and unstimulated salivary flow rate increased from (0.65±0.46) to (0.78±0.45) (P=0.011) in the TGP group, but the placebo group showed no significant difference. Erythrocyte sedimentation rate (ESR) was decreased significantly compared to the placebo group at 12- and 24-week from (40.9±18.0) to (29.4±12.2) (P=0.003) and (30.4±17.3) (P=0.024). The percentage of naive B cells decreased at week 24 in the TGP group from (77.34±12.20) to (64.59±15.60) (P=0.005) while memory B cells increased from (21.79±11.97) to (34.21±15.48) (P=0.006) respectively. The concentrations of TNF-α and IFN-γ decreased in the TGP group at week 24 from (32.51±26.67) to (24.22±13.56) (P=0.017) and (10.71±8.94) to (6.55±4.88) (P=0.022), respectively. No significant difference in ANA titer, anti-SSA antibodies, anti-SSB antibodies, C3 concentration or C4 concentration was observed between the two groups.

CONCLUSION

TGP appears to improve the glandular secreting function and decrease the level of inflammatory cytokines.

Early BAFF receptor blockade mitigates murine Sjögren's syndrome: Concomitant targeting of CXCL13 and the BAFF receptor prevents salivary hypofunction

Sjögren's syndrome (SS) is a debilitating autoimmune disease. Patients with SS may develop xerostomia. This process is progressive, and there are no therapeutics that target disease etiology. We hypothesized BAFF receptor (BAFFR) blockade would mitigate SS disease development, and neutralization of CXCL13 and BAFF signaling would be more efficacious than BAFFR blockade alone. We treated NOD/ShiLtJ SS mice with soluble BAFF receptor (BAFFR-Fc) or anti-CXCL13/BAFFR-Fc in combination, prior to the development of clinical disease. Our results show treatment with BAFFR-Fc reduced peripheral B cell numbers and decreased sialadenitis. In addition, this treatment reduced total serum immunoglobulin as well as IgG and IgM specific anti-nuclear autoantibodies. NOD/ShiLtJ mice treated with BAFFR-Fc and anti-CXCL13 antibody were protected from salivary deficits. Results from this study suggest blockade of CXCL13 and BAFFR together may be an effective therapeutic strategy in preventing salivary hypofunction and reducing autoantibody titers and sialadenitis in patients with SS.

Polychromatic flow cytometry in evaluating rheumatic disease patients

B cells are central players in multiple autoimmune rheumatic diseases as a result of the imbalance between pathogenic and protective B-cell functions, which are presumably mediated by distinct populations. Yet the functional role of different B-cell populations and the contribution of specific subsets to disease pathogenesis remain to be fully understood owing to a large extent to the use of pauci-color flow cytometry. Despite its limitations, this approach has been instrumental in providing a global picture of multiple B-cell abnormalities in multiple human rheumatic diseases, more prominently systemic lupus erythematosus, rheumatoid arthritis and Sjogren’s syndrome. Accordingly, these studies represent the focus of this review. In addition, we also discuss the added value of tapping into the potential of polychromatic flow cytometry to unravel a higher level of B-cell heterogeneity, provide a more nuanced view of B-cell abnormalities in disease and create the foundation for a precise understanding of functional division of labor among the different phenotypic subsets. State-of-the-art polychromatic flow cytometry and novel multidimensional analytical approaches hold tremendous promise for our understanding of disease pathogenesis, the generation of disease biomarkers, patient stratification and personalized therapeutic approaches.