B cell subsets and dysfunction of regulatory B cells in IgG4-related diseases and primary Sjögren's syndrome: the similarities and differences

The role of fatty acid metabolism on B cells and B cell-related autoimmune diseases

Fatty acid metabolism plays a critical role in regulating immune cell function, including B cells, which are central to humoral immunity and the pathogenesis of autoimmune diseases. Emerging evidence suggests that fatty acid metabolism influences B cell development, activation, differentiation, and antibody production, thereby impacting B cell-related autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and multiple sclerosis (MS). In this review, we discuss the mechanisms by which fatty acid metabolism modulates B cell biology, including energy provision, membrane composition, and signaling pathways. We highlight how alterations in fatty acid synthesis, oxidation, and uptake affect B cell function and contribute to autoimmune pathogenesis. Additionally, we explore the therapeutic potential of targeting fatty acid metabolism in B cells to treat autoimmune diseases. Understanding the interplay between fatty acid metabolism and B cell immunity may provide novel insights into the development of precision therapies for B cell-mediated autoimmune disorders.

Regulatory B cells in autoimmune diseases: Insights and therapeutic potential

Autoimmune diseases are characterized by the body's immune system attacking its own cells, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and multiple sclerosis (MS). In recent studies, regulatory B cells (Bregs), which play a vital role in maintaining peripheral tolerance and controlling persistent autoimmune diseases (ADs), have shown great potential in treating ADs. This review synthesizes the latest advancements in targeted therapies for ADs, with a particular emphasis on the subgroups, phenotypic markers, and signal pathways associated with Bregs. Following an examination of these elements, the discussion pivots to innovative Breg-based therapeutic approaches for the management of ADs.

Immune Cell Profiles of Patients with Sickle Cell Disease during Parvovirus B19-Induced Transient Red Cell Aplasia

Parvovirus B19 frequently infects children and targets cells of the erythroid lineage. Although healthy children rarely suffer severe disease, children with sickle cell disease (SCD) can experience transient red cell aplasia (TRCA), hospitalization, and life-threatening anemia upon first virus exposure. Given that children with SCD can also suffer chronic inflammation and that parvovirus B19 has been associated with autoimmune disease in other patient populations, we asked if parvovirus B19 infections contributed to acute and chronic immune abnormalities in children with SCD. Nineteen hospitalized patients with SCD and parvovirus B19-induced TRCA were evaluated. Blood tests included CBC, flow cytometry, and total antibody isotype analyses. Cytokine/chemokine analyses were performed on nasal wash (NW) samples, representing a common site of viral entry. Unusually high white blood cell count (WBC) and absolute neutrophil count (ANC) values were observed in some patients. A correlation matrix with Day 0 values from the 19 patients then identified two mutually exclusive phenotype clusters. Cluster 1 included WBC, ANC, absolute reticulocyte count (ARC), absolute lymphocyte count (ALC), lactate dehydrogenase (LDH), NW cytokines/chemokines, % naïve cells among B cell and T cell populations, and parvovirus-specific IgG. This cluster was negatively associated with virus load, suggesting a signature of successful adaptive immunity and virus control. Cluster 2 included virus load, % CD38+CD24- cells among CD19+ B cells (termed 'plasmablasts' for simplicity), % HLA-DRlow cells among CD19+ B cells, IgG4, and % memory phenotypes among B cell and T cell populations. Plasmablast percentages correlated negatively with parvovirus-specific IgG, possibly reflecting a non-specific trigger of cell activation. All patients were released from the hospital within 1 week after admission, and the highest WBC and ANC values were eventually reduced. Nonetheless, a concern remained that the acutely abnormal immune profiles caused by parvovirus B19 infections could exacerbate chronic inflammation in some patients. To avoid the numerous sequelae known to affect patients with SCD following hospitalizations with parvovirus B19, rapid development of a parvovirus B19 vaccine is warranted.

Bayesian-based analysis of the causality between 731 immune cells and erectile dysfunction: a two-sample, bidirectional, and multivariable Mendelian randomization study

Background

The causal relationship between certain immune cells and erectile dysfunction (ED) is still uncertain.

Aim

The study sought to investigate the causal effect of 731 types of immune cells on ED through Mendelian randomization (MR) using genome-wide association studies (GWAS).

Methods

Genetic instruments for 731 immune cells were identified through GWAS, and ED data were obtained from the FinnGen database. Univariable and multivariable bidirectional MR studies were conducted to explore potential causal relationships between these immune cells and ED. The inverse-variance weighted method was primarily used, with Cochran's Q test and MR-Egger intercept test assessing pleiotropy and heterogeneity. Bayesian weighted Mendelian randomization (BWMR) was also employed.

Outcomes

Six immune cells were identified as related to ED. CD45 on Natural Killer (NK) cells, CD33dim HLA DR+ CD11b + Absolute Count, CD19 on IgD- CD38dim B cells, and CD3 on CD39+ resting CD4 regulatory T cells were identified as risk factors, whereas CD20 on IgD+ CD38dim B cells and Activated & resting CD4 regulatory T cell %CD4+ T cells were protective factors. Further multivariable MR analysis confirmed that 5 of these immune cells independently impacted ED, except for CD45 on NK cells. Reverse MR analysis indicated that ED occurrence decreases certain immune cell counts, but BWMR found no causal relationship for CD20 on IgD+ CD38dim B cells.

Results

Our MR analysis confirmed a potential bidirectional causal relationship between immune cells and ED, providing new insights into potential mechanisms and therapeutic strategies.

Clinical Translation

This study provides evidence for the impact of certain immune cells on the development of ED and suggests potential therapeutic targets.

Strengths and Limitations

We performed both univariable and multivariable MR to strengthen the causal relationship between exposures and outcomes. However, the population in this study was limited to European ancestry.

Conclusion

Our MR analysis confirmed a potential bidirectional causal relationship between immune cells and ED. This provides new insights into potential mechanisms of pathogenesis and subsequent therapeutic strategies.

Profiles of peripheral B cell subsets in a cohort of primary Sjögren's syndrome patients and their potential clinical significance

Background/purpose

Primary Sjögren's syndrome is a prototypical autoimmune disease, with B cell dysfunction as a dominant feature. Further insights into distribution of B cell subsets in primary Sjögren's syndrome are urgently required to identify the most appropriate target subpopulation. We aimed to evaluate the profiles of B lymphocyte subpopulations in primary Sjögren's syndrome patients and to investigate their clinical significance.

Materials and methods

Thirty primary Sjögren's syndrome patients and 15 age-and sex-matched healthy controls were recruited. Peripheral B cell subsets were analyzed by flow cytometry.

Results

Compared to healthy controls, circulating CD19+ B cells, CD19+CD20- B cells, CD19+CD27-IgD+ naïve B cells, CD19+IgD+CD38high plasmablasts, CD19+CD24highCD38high transitional B cells and CD19+CD20-CD27+CD38+ plasma cells were elevated in patients with primary Sjögren's syndrome, whereas CD19+CD27+ memory B cells, CD19+CD27-IgD- double negative B cells and CD19+CD24hiCD27+ Bregs were decreased. Furthermore, the percentage of circulating CD19+CD20-CD27+CD38+ plasma cells was positively correlated with serum IgG levels and the proportional area of lymphocytic infiltration of labial gland.

Conclusion

We identified a comprehensive B lymphocyte subset distribution profile in primary Sjögren's syndrome. Moreover, we detected a clinical significance of CD19+CD20-CD27+CD38+ plasma cells, suggesting that these cells might play a key role in disease pathology and represent potential therapeutic targets.

Viral DNA in submandibular gland tissue with an inflammatory disorder

Background

The etiology behind different types of chronic sialadenitis (CS), some of which exhibit IgG4 overexpression, is unknown. Further, IgG4-related disease (IgG4-RD) commonly affects the submandibular gland, but its relationship to IgG4-overexpressing CS, and the antigen triggering IgG4 overexpression, remain unknown.

Materials and Methods

By qPCR, we assessed the presence of 21 DNA-viruses causing IgG4 overexpression in submandibular gland tissue from patients with IgG4-positive and IgG4-negative CS. Healthy submandibular glands and glands with sialolithiasis without CS were used as controls. We examined the distribution of HHV-7, HHV-6B and B19V DNA, within virus PCR-positive tissues with RNAscope in-situ hybridization (RISH).

Results

We detected DNA from seven viruses in 48/61 samples. EBV DNA was more prevalent within the IgG4-positive samples (6/29; 21%) than the IgG4-negative ones (1/19; 5.3%). B19V DNA was more prevalent within the IgG4-negative samples (5/19; 26%) than the IgG4-positive ones (4/29; 14%). The differences in virus prevalence were not statistically significant. Of the IgG4-RD samples (n = 3) one contained HHV-6B DNA. RISH only showed signals of HHV-7.

Conclusions

None of the studied viruses are implicated as triggering IgG4-overexpression in CS. Although our results do not confirm viral etiology in the examined conditions, they provide valuable information on the prevalence of viruses in both diseased and healthy submandibular gland tissue.

B Cells Dynamic in Aging and the Implications of Nutritional Regulation

Aging negatively affects B cell production, resulting in a decrease in B-1 and B-2 cells and impaired antibody responses. Age-related B cell subsets contribute to inflammation. Investigating age-related alterations in the B-cell pool and developing targeted therapies are crucial for combating autoimmune diseases in the elderly. Additionally, optimal nutrition, including carbohydrates, amino acids, vitamins, and especially lipids, play a vital role in supporting immune function and mitigating the age-related decline in B cell activity. Research on the influence of lipids on B cells shows promise for improving autoimmune diseases. Understanding the aging B-cell pool and considering nutritional interventions can inform strategies for promoting healthy aging and reducing the age-related disease burden.

The spectrum of B cells in the pathogenesis, diagnosis and therapeutic applications of immunoglobulin G4-related disease

Immunoglobulin G4 (IgG4)-related disease is a chronic fibroinflammatory disease mediated by immune disorders. Given the challenging clinical diagnosis and treatment, knowledge of the pathogenesis of IgG4-related disease is important. The typical elevation of serum IgG4 concentrations and infiltration of IgG4-positive plasma cells in the involved tissues indicate the involvement of B lymphocytes in the pathogenesis of IgG4-related disease. Mass production of autoantibodies reflects abnormal activation of B cells, which causes tissue damage. Circulating plasmablasts are recently discovered markers that correlate with serum IgG4 concentration, the extent of organ involvement and disease activity. B-cell depletion therapy is an emerging curative strategy that can significantly alleviate clinical manifestations and achieve remission in patients with IgG4-related disease. These findings highlight the potential role of B cells in IgG4-related disease. In this review, we discuss the pathogenic impact of B lymphocytes on IgG4-related disease and describe novel therapies targeting B cells.

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.

Peripheral Immunophenotype in IgG4-Related Disease and Its Association with Clinical Phenotypes and Disease Activity

Diverse immune cell subsets have been described in IgG4-related disease (IgG4-RD). If there is a different immunophenotype according to clinical phenotype and activity status is not known. Levels of IL-4-, IL-13-, IL-5-, and IL-21-producing CD4+ T cells (Th2 subsets), CD4+ cytotoxic T lymphocytes (CD4+CTLs), T helper 9 cells, T follicular helper cells (Tfh; Tfh1/Tfh2/Tfh17/Tf regulatory [Tfr]), Foxp3+ regulatory T cells, Type 1 regulatory T cells (Tr1), T helper 3 regulatory cells (Th3), IL-10-producing regulatory B cells (Bregs), IL-10-expressing regulatory plasmacytoid dendritic (pDC IL-10+) cells, and M1 and M2 monocytes were determined by flow cytometry in 43 IgG4-RD patients and 12 controls. All immune subsets were higher in patients vs. controls. CD4+/IL-4+, CD4+/IL-5+, CD4+CTLs, Tfh2, Tfh17, Tfr, and M1 monocyte cell number was different among IgG4-RD clinical phenotypes. The pancreato-hepato-biliary phenotype was characterized by a higher CD4+CTLs, Tfh17, Tfh2, and Tfr and lower M1 cell number. An increased CD4+CTLs and Th3 cell number distinguished the head and neck-limited phenotype, while the retroperitoneal/aortic and Mikulicz/systemic phenotypes were characterized by increased Th2 subsets. Tfh17, Tr1, Th3, pDC, M1, and M2 monocytes were augmented in active patients. In summary, the clinical heterogeneity of IgG4-RD might be driven by the participation of different immunophenotypes and, consequently, by a different fibroinflammatory process.

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.

IgG4-related brain pseudotumor mimicking CNS lymphoma. A case report

Here, we report a case of IgG4-related brain pseudotumor (IgG4-BP) in a 39-year-old woman, mimicking central nervous system (CNS) lymphoma. She presented with headache, fever, and fatigue. Her medical history was notable for appearance of a tumefactive brain lesion seven years before. Brain biopsy performed at the age of 32 revealed nonspecific inflammatory changes, and her condition improved with oral low-dose steroid therapy. Magnetic resonance imaging performed at the age of 39 identified a hyperintensity lesion with edema located at the medial temporal lobe region adjacent to the inferior horn of the left lateral ventricle on fluid-attenuated inversion recovery images, which showed gadolinium-contrast enhancement on T1-weighted images and a slightly hyperintensity signal on diffusion-weighted images. Methionine-positron emission tomography (PET) depicted a high methionine uptake in the lesion. Additionally, soluble levels of interleukin (IL)-2 receptor (sIL-2R) and IL-10 were increased in cerebrospinal fluid (CSF). Based on these findings, we suspected CNS lymphoma and performed partial resection of the brain lesion. Pathological examination revealed prominent lymphocytic infiltration associated with plasma cell infiltration. Most of the plasma cells were immunoreactive for IgG4. Storiform fibrosis and partially obliterative phlebitis were concomitantly observed. Thus, the patient was diagnosed as having IgG4-BP. To the best of our knowledge, this is the first case report of IgG4-BP with detailed findings obtained by CSF testing, methionine-PET, and pathological examination. Because IgG4-related diseases can present as a pseudotumor that mimics CNS lymphoma, it is essential to carefully differentiate IgG4-BP from CNS lymphoma.

The landscape of T and B lymphocytes interaction and synergistic effects of Th1 and Th2 type response in the involved tissue of IgG4-RD revealed by single cell transcriptome analysis

OBJECTIVES

To investigate the landscape of T-B cell interaction, immune receptor profiles and effects of different types of immune responses in the involved tissues of IgG4-RD.

METHODS

Single cell RNA sequencing, bulk sample RNA sequencing, immune receptor repertoire analysis (both BCR and TCR), multi-color flow cytometry, and in-vitro assays with model cells (e.g. EBV-immortalized B cells from IgG4-RD patient) and histologic methods were applied to investigate the immunopathological features of IgG4-RD from multiple aspects.

RESULTS

Ectopic germinal center formation was observed in IgG4-RD patients at advanced disease stage, and a large part of B cells in involved tissue were germinal center B cell-like. Germinal center reaction in IgG4-RD led to the irregularities of both TCR and BCR clones in the involved tissues, and limited clonal overlaps among different samples. Enhanced Th1- and Th2-type responses were observed in involved tissues of IgG4-RD and patients with both increased Th1- and Th2-type response related cell subsets possessed more severe inflammatory indices. Analyses to the origin of IGHG4 transcripts in IgG4-RD indicated that IgG4 could be switched from IgM directly, or from other IgG subclasses. In vitro assays with EBV-immortalized B cells, fibroblasts and epithelial cells revealed the effects of Th1-type and Th2-type responses on germinal center reaction, ectopic expression of MHC-II molecules, and formation of tertiary lymphoid structures.

CONCLUSIONS

Synergistic effects of Th1- and Th2-type responses were involved in the pathogenesis of IgG4-RD via their influences on both acute inflammatory processes and the chronicity and complexity of IgG4-RD.

Potential roles of non-lymphocytic cells in the pathogenesis of IgG4-related disease

Studies have confirmed the involvement of a variety of lymphocyte subsets, including type 2 helper T lymphocytes (Th2) and IgG4+ B lymphocytes, in the pathogenesis of IgG4-related disease (IgG4-RD). Those lymphocytes contribute to the major pathogenetic features of IgG4-RD. However, they are not the only cellular components in the immunoinflammatory environment of this mysterious disease entity. Recent studies have suggested that various non-lymphocytic components, including macrophages and fibroblasts, may also play an important role in the pathogenetic process of IgG4-RD in terms of contributing to the chronic and complex progress of the disease. Therefore, the potential role of non-lymphocyte in the pathogenesis of IgG4-RD is worth discussing.

Hypocomplementemia in primary Sjogren’s syndrome: association with serological, clinical features, and outcome

Objective

The aim of the present study was to assess the clinical characteristic of hypocomplementemia (HC) in primary Sjogren’s syndrome (pSS), and to address possible risk factors and the prognosis associated with HC in pSS patients.

Methods

pSS patients with HC in Hebei General Hospital from September 2016 to March 2019 were retrospectively analyzed and compared to those with normocomplementemia (NC). Logistic regression analysis was used to detect risk factors.

Results

Of the 333 patients with pSS, 84 patients (25.23%) were presented with HC at diagnosis. The presence of hyper-IgG and anti-Ro52 antibodies was significantly more common in patients with HC. In addition to systemic involvement, pSS patients with HC had more hematological, renal, and nervous system involvement, and received more immunosuppressant treatments than NC group (p < 0.05). ESSDAI score was significantly higher in patients with HC (p < 0.05). Multivariate logistic analysis indicated that leukopenia (OR = 2.23) and hyper-IgG (OR = 2.13) were independent risk factors for pSS with HC. In addition, profound CD16/CD56+ NK-cell lymphopenia was found in pSS-HC patients. More pSS patients developed SLE in the HC group than NC group (4.76% vs. 0.80%, p = 0.04) during the follow-up.

Conclusion

HC was not an uncommon manifestation of pSS and had an independent association with the main clinical and immunological features. Patients with pSS-HC had an increased possibility to develop SLE that required more positive treatment with glucocorticoids and immunosuppressants.

Key Points:

• Hypocomplementemia had an independent association with the main clinical and immunological features in primary Sjogren’s syndrome patients.

• ESSDAI score was significantly higher in patients with hypocomplementemia.

• The pSS patients with hypocomplementemia had an increased possibility to develop SLE.

Interstitial lung disease in Primary Sjögren's syndrome

Background

Interstitial lung disease (ILD) may cause life-threatening complications of primary Sjogren’s syndrome (pSS), and has a poor prognosis in terms of survival and quality of life. To date, few studies have investigated the risk factors for ILD detected by high-resolution computed tomography (HRCT) in pSS patients with or without respiratory symptoms.

Methods

Data of 333 patients with newly diagnosed pSS were retrospectively analysed. Interstitial lung disease involvement was defined as typical abnormalities on HRCT and/or pulmonary function tests. Multivariate regression model was used to evaluate the association between interstitial lung disease and pSS characteristics.

Results

Sixty-six patients (19.82%) were diagnosed with pSS-ILD. Ground glass opacities (87.88%) and septal/sub pleural lines (81.82%) were most frequent. Based on pulmonary high-resolution computed tomography, patients were divided into nonspecific (n = 42), usual (n = 20), lymphocytic interstitial pneumonia (n = 3) and cryptogenic organising pneumonia (n = 1) groups. There was a strong association between erythrocyte sedimentation rate (ESR)/C-reactive protein (CRP) and the HRCT-score. Pulmonary function tests revealed impaired diffusion capacity for carbon monoxide and total lung capacity, and coexistence of small airway lesions in pSS-interstitial lung disease. On logistic regression analysis, age, Raynaud’s phenomenon, lymphopenia, cough, dyspnoea and rampant dental caries were risk factors associated with pSS-interstitial lung disease.

Conclusions

Interstitial lung disease involvement in pSS is a common clinical occurrence. The clinical manifestation is nonspecific and variable; Raynaud’s phenomenon and lymphopenia may predict its onset. pSS patients with advanced age, dry cough and dyspnoea should be systematically evaluated for ILD involvement and managed according to their symptoms.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-01868-5.

Orchestration of Immune Cells Contributes to Fibrosis in IgG4-Related Disease

This review summarizes recent progress in understanding the pathogenesis of IgG4-related disease (IgG4-RD), with a focus on fibrosis. Several studies reported that CD4+ T cells with cytotoxic activity promoted by the secretion of granzyme and perforin, cytotoxic CD4+ T cells (CD4+CTLs), and disease-specific activated B cells, infiltrated inflamed tissues and cooperated to induce tissue fibrosis in autoimmune fibrotic diseases such as IgG4-RD, systemic sclerosis, and fibrosing mediastinitis. An accumulation of cells undergoing apoptotic cell death induced by CD4+CTLs and CD8+CTLs followed by macrophage-mediated clearing and finally tissue remodeling driven by cytokines released by CD4+CTLs, activated B cells, and M2 macrophages may contribute to the activation of fibroblasts and collagen production. In IgG4-RD, this process likely involves the apoptosis of non-immune, non-endothelial cells of mesenchymal origin and subsequent tissue remodeling. In summary, CD4+CTLs infiltrate affected tissues where they may cooperate with activated B cells, CD8+CTLs, and M2 macrophages, to induce apoptosis by secreting cytotoxic cytokines. These immune cells also drive fibrosis by secreting pro-fibrotic molecules in IgG4-RD.

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.

Altered B cell compartment associated with Tfh cells in children with Henoch-Schonlein Purpura

AIM

IgA-producing B cells have been found to be associated with children diagnosed with Henoch-Schonlein purpura (HSP). The aim of the present study was to determine whether children with HSP possess altered B-cell subsets.

METHODS

A total of 14 children diagnosed with HSP and age- and sex-matched healthy controls (HCs) were enrolled in our study. Peripheral blood mononuclear cells were isolated, and the percentage and absolute number of B-cell subsets and Follicular helper T (Tfh) cells were determined by flow cytometry. Finally, Spearman's correlation coefficient was used to analyse the correlation between the percentage of Tfh cells and B-cell subsets.

RESULTS

We found that compared to HCs, the frequency and absolute number of total B cells were significantly higher in children with HSP, but the percentages of plasma cells and naïve B cells were significantly lower. A significantly increased percentage and absolute number of memory nonswitched B cells were found in children with HSP compared with HCs. We observed that the expression of C-X-C chemokine receptor type 5 (CXCR5) on total CD4⁺ T cells and the percentage of CD4⁺CXCR5⁺ cells were significantly increased in patients with HSP. Moreover, significantly correlations between Tfh cells and various B-cell subsets were observed.

CONCLUSIONS

Our study showed a Tfh-cell-associated altered B cell compartment in children with HSP.

IgG4-related disease and idiopathic multicentric Castleman's disease: confusable immune-mediated disorders

IgG4-related disease (IgG4-RD) and idiopathic multicentric Castleman's disease (iMCD) are both rare systemic immune-mediated disorders. However, pathogenesis differs markedly between the two diseases, and differing therapeutic strategies are adopted: IgG4-RD is treated using a moderate dose of glucocorticoids or rituximab, while iMCD therapy involves an interleukin (IL)-6 targeted approach. Nonetheless, some clinical features of IgG4-RD and iMCD overlap, so differential diagnosis is sometimes difficult, even though the classification and diagnostic criteria of the diseases require careful exclusion of the other. The key findings in IgG4-RD are high IgG4/IgG ratio, allergic features, and germinal centre expansion involving T follicular helper cells, while iMCD involves polyclonal antibody production (high IgA and IgM levels), sheet-like mature plasma cell proliferation, and inflammatory features driven by IL-6. The distribution of organ involvement also provides important clues in both diseases. Particular attention should be given to differential diagnosis using combined clinical and/or pathological findings, because single features cannot distinguish IgG4-RD from iMCD. In the present review, we discuss the similarities and differences between IgG4-RD and iMCD, as well as how to distinguish the two diseases.

Differences in clinical characteristics of IgG4-related disease across age groups: a prospective study of 737 patients

OBJECTIVE

The aim of this study was to compare the clinical characteristics of IgG4-related disease (IgG4-RD) among different age groups.

METHODS

We conducted a prospective study of 737 patients who were newly diagnosed with IgG4-RD and compared detailed demographic features, organ involvements, laboratory tests, treatments and outcomes across age groups. The patients were divided into five groups according to their age at diagnosis: ≤39, 40-49, 50-59, 60-69 and ≥70 years. The clinical characteristics of paediatric patients were also described.

RESULTS

Sex ratio, disease duration, allergy history and clinical symptoms were significantly different across age groups. Besides, the proportions of superficial organ involvement (lacrimal gland and sinus) decreased with age, while the proportions of internal organ involvement (pancreas, biliary tract, retroperitoneal tissue, lung and prostate) increased with age, which was more prominent in male patients. Mikulicz's disease was the most common manifestation (70%) in paediatric IgG4-RD patients. Multiple Cox analysis identified that age ≤56 years at diagnosis was an independent risk factor of relapse.

CONCLUSION

We revealed the impact of age on clinical characteristics of IgG4-RD, which indicated that different management might be required among different age groups.

The Multiple Roles of B Cells in the Pathogenesis of Sjögren's Syndrome

Primary Sjögren’s syndrome (pSS) is a chronic autoimmune disease characterized by lymphocytic infiltration and tissue destruction of exocrine glands such as salivary glands. Although the formation of ectopic lymphoid tissue in exocrine glands and overproduction of autoantibodies by autoreactive B cells highlight the critical involvement of B cells in disease development, the precise roles of various B cell subsets in pSS pathogenesis remain partially understood. Current studies have identified several novel B cell subsets with multiple functions in pSS, among which autoreactive age-associated B cells, and plasma cells with augmented autoantibody production contribute to the disease progression. In addition, tissue-resident Fc Receptor-Like 4 (FcRL4)⁺ B cell subset with enhanced pro-inflammatory cytokine production serves as a key driver in pSS patients with mucosa-associated lymphoid tissue (MALT)-lymphomas. Recently, regulatory B (Breg) cells with impaired immunosuppressive functions are found negatively correlated with T follicular helper (Tfh) cells in pSS patients. Further studies have revealed a pivotal role of Breg cells in constraining Tfh response in autoimmune pathogenesis. This review provides an overview of recent advances in the identification of pathogenic B cell subsets and Breg cells, as well as new development of B-cell targeted therapies in pSS patients.

The Role of Regulatory B cells in Kidney Diseases

B cells, commonly regarded as proinflammatory antibody-producing cells, are detrimental to individuals with autoimmune diseases. However, in recent years, several studies have shown that regulatory B (Breg) cells, an immunosuppressive subset of B cells, may exert protective effects against autoimmune diseases by secretion of inhibitory cytokines such as IL-10. In practice, Breg cells are identified by their production of immune-regulatory cytokines, such as IL-10, TGF-β, and IL-35, however, no specific marker or Breg cell-specific transcription factor has been identified. Multiple phenotypes of Breg cells have been found, whose functions vary according to their phenotype. This review summarizes the discovery, phenotypes, development, and function of Breg cells and highlights their potential therapeutic value in kidney diseases.

The Role of PD-1/PD-Ls in the Pathogenesis of IgG4-RD

OBJECTIVE

To investigate the role of Programmed cell death protein 1 (PD-1) and its two ligands PD-L1 and PD-L2 in the pathogenesis of IgG4-RD.

METHODS

Patients with IgG4-RD (n = 43) as well as healthy controls (n = 34) were recruited. Expression levels of PD-1, PD-L1 and PD-L2 in plasma, submandibular gland and T cell subsets were determined by ELISA, immunohistochemistry and flow cytometry. Naive T cells were stimulated with or without PD-L1/PD-L2 or anti-PD-L1/anti-PD-L2 for 7 days and the proportion of CD4+CD25+Treg cells was detected by flow cytometry.

RESULTS

The expression of PD-1, PD-L1 and PD-L2 in the plasma, submandibular gland and on the surface of Treg cells were increased in IgG4-RD patients. Plasma sPD-1 was positively correlated with serum IgG, IgG1, IgG3, IgG4, IgG4-RD RI and numbers of organs involved, and negatively correlated with serum IgM, IgA, C3 and C4. Plasma sPD-L2 was positively correlated with serum IgG1, plasma sPD-L1 was positively correlated with sPD-L2 and negatively correlated with C3. Stimulation of PD-L1 but not PD-L2 promoted the differentiation of naive T cells from IgG4-RD patients into CD4+CD25+Treg cells.

CONCLUSION

Plasma concentration of sPD-1, sPD-L1 and sPD-L2 were significantly increased in patients with IgG4-RD, and the expression of PD-1 and PD-L2 on Treg cells were upregulated. PD-1/PD-L1 can promote the differentiation of naive T cells into Treg cells and thus participate in the pathogenesis of IgG4-RD.

Clinical features and risk factors of Raynaud's phenomenon in primary Sjögren's syndrome

Objective

The aim at the current study was to investigate the clinical characteristics and risk factors of Raynaud’s phenomenon (RP) in patients with primary Sjögren’s syndrome (pSS).

Methods

Retrospective analysis of the medical records of 333 new-onset pSS patients was performed. Demographic, clinical, and serological data were compared between individuals with and without RP. Logistic regression analysis was used to identify risk factors.

Results

RP was present in 11.41% of the pSS patients. pSS-RP patients were younger (49.74±14.56 years vs. 54.46±13.20 years, p=0.04) and exhibited higher disease activity (11 [5.75–15] vs. 7 [4–12], p=0.03) than those without. The prevalence of lung involvement was significantly higher in pSS patients with RP (60.53% vs. 17.29%; p<0.001). A significantly higher proportion of patients with pSS-RP tested positive about antinuclear (ANA), anti-RNP, and anti-centromere antibodies (ACA) compared to those without (p=0.003, <0.001, and 0.01, respectively). Multivariate analysis identified lung involvement (odds ratio [OR]=8.81, 95% confidence interval [CI] 2.02–38.47; p=0.04), anti-RNP positive status (OR=79.41, 95% CI 12.57–501.78; p<0.0001), as well as ACA (OR=13.17, 95% CI 2.60–66.72; p=0.002) as prognostic factors for pSS-RP.

Conclusion

The presence of RP defined a subset of pSS with a unique phenotype, manifesting as increased lung involvement and a higher frequency of anti-RNP antibodies and ACA, as well as greater disease activity. These results suggest that RP has clinical and prognostic value of pSS patients. Further prospective studies with a larger number of subjects are warranted to confirm our findings and assess the prognostic and treatment implications of RP in pSS patients.

Key Points • Raynaud’s phenomenon (RP) was present in 38 (11.41%) of 333 patients with primary Sjögren’s syndrome (pSS), with patients with RP exhibiting a younger age and higher disease activity. • The presence of RP indicates a subset of pSS with a unique phenotype, with manifestations including increased lung involvement and a higher frequency of anti-RNP antibodies and anti-centromere antibodies. • Patients with pSS and RP need close follow-up and long-term observation (including assessment of microangiopathy), with specific attention paid to the possible development of clinical features of systemic sclerosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10067-021-05749-w.

Advances of Regulatory B Cells in Autoimmune Diseases

With the ability to induce T cell activation and elicit humoral responses, B cells are generally considered as effectors of the immune system. However, the emergence of regulatory B cells (Bregs) has given new insight into the role of B cells in immune responses. Bregs exhibit immunosuppressive functions via diverse mechanisms, including the secretion of anti-inflammatory cytokines and direct cell contact. The balance between Bregs and effector B cells is important for the immune tolerance. In this review, we focus on recent advances in the characteristics of Bregs and their functional roles in autoimmunity.

The Role of B Cells and B Cell Therapies in Immune-Mediated Liver Diseases

B cells form a branch of the adaptive immune system, essential for the body’s immune defense against pathogens. B cell dysfunction has been implicated in the pathogenesis of immune mediated liver diseases including autoimmune hepatitis, IgG4-related hepatobiliary disease, primary biliary cholangitis and primary sclerosing cholangitis. B cells may initiate and maintain immune related liver diseases in several ways including the production of autoantibodies and the activation of T cells via antigen presentation or cytokine production. Here we comprehensively review current knowledge on B cell mechanisms in immune mediated liver diseases, exploring disease pathogenesis, B cell therapies, and novel treatment targets. We identify key areas where future research should focus to enable the development of targeted B cell therapies.

Regulatory B cells in respiratory health and diseases

B cells are critical mediators of humoral immune responses in the airways through antibody production, antigen presentation, and cytokine secretion. In addition, a subset of B cells, known as regulatory B cells (Bregs), exhibit immunosuppressive functions via diverse regulatory mechanisms. Bregs modulate immune responses via the secretion of IL‐10, IL‐35, and tumor growth factor‐β (TGF‐β), and by direct cell contact. The balance between effector and regulatory B cell functions is critical in the maintenance of immune homeostasis. The importance of Bregs in airway immune responses is emphasized by the different respiratory disorders associated with abnormalities in Breg numbers and function. In this review, we summarize the role of immunosuppressive Bregs in airway inflammatory diseases and highlight the importance of this subset in the maintenance of respiratory health. We propose that improved understanding of signals in the lung microenvironment that drive Breg differentiation can provide novel therapeutic avenues for improved management of respiratory diseases.

Interleukin-35 regulates the balance of Th17 and Treg responses during the pathogenesis of connective tissue diseases

Interleukin (IL)-35 belongs to the IL-12 cytokine family and is a heterodimer of the p35 and Epstein-Barr virus-induced gene 3 (EBI3) subunits. Functionally, IL-35 can promote the proliferation and activation of regulatory T cells (Tregs) and suppress the function of T helper 17 (Th17) cells and other inflammatory cells to inhibit immune responses. In recent years, an abnormal IL-35 expression causing a Th17/Treg imbalance has been associated with the development and progression of several connective tissue diseases (CTDs), such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic sclerosis (SSc), dermatomyositis (DM)/polymyositis (PM), and primary Sjögren's syndrome (pSS). Here, we review the role of IL-35 in regulating the balance of Th17/Treg responses in different types of CTDs and provide new insights into the role of IL-35 in these diseases.

The Cellular and Molecular Bases of Allergy, Inflammation and Tissue Fibrosis in Patients with IgG4-related Disease

IgG4-related disease (IgG4-RD) is a spectrum of complex fibroinflammatory disorder with protean manifestations mimicking malignant neoplasms, infectious or non-infectious inflammatory process. The histopathologic features of IgG4-RD include lymphoplasmacytic infiltration, storiform fibrosis and obliterative phlebitis together with increased in situ infiltration of IgG4 bearing-plasma cells which account for more than 40% of all IgG-producing B cells. IgG4-RD can also be diagnosed based on an elevated serum IgG4 level of more than 110 mg/dL (normal < 86.5 mg/mL in adult) in conjunction with protean clinical manifestations in various organs such as pancreato–hepatobiliary inflammation with/without salivary/lacrimal gland enlargement. In the present review, we briefly discuss the role of genetic predisposition, environmental factors and candidate autoantibodies in the pathogenesis of IgG4-RD. Then, we discuss in detail the immunological paradox of IgG4 antibody, the mechanism of modified Th2 response for IgG4 rather than IgE antibody production and the controversial issues in the allergic reactions of IgG4-RD. Finally, we extensively review the implications of different immune-related cells, cytokines/chemokines/growth factors and Toll-like as well as NOD-like receptors in the pathogenesis of tissue fibro-inflammatory reactions. Our proposals for the future investigations and prospective therapeutic strategies for IgG4-RD are shown in the last part.

Association of salivary inflammatory biomarkers with primary Sjögren's syndrome

BACKGROUND

Primary Sjogren's syndrome (pSS) is an autoimmune disease that leads to salivary and lacrimal gland dysfunction. The adaptive immune response associated with T helper-2 lymphocytes appears to be altered in these patients. Therefore, the objective of this study was to determine the salivary levels of interleukin (IL)-6, IL-5, and IL-4 in patients with pSS when compared to a healthy control (HC) group. The secondary objectives were to study whether ILs levels in pSS patients were associated with salivary flow, patient-reported outcomes (PROMs) for xerostomia and oral health quality of life (Oral Health Impact Profile-14 [OHIP-14]), pSS classification criteria and presence of extraglandular manifestations.

METHODS

A case-control study was conducted in 36 patients with pSS and 35 HCs. Cytokine levels were measured using high-sensitivity multiplex map human immunoassays. Unstimulated and stimulated whole saliva were collected and patients filled out questionnaires. The Mann-Whitney U test, chi-squared test, and Spearman correlation test were used.

RESULTS

Interleukin-6 was significantly higher in pSS patients than in HCs (P = .0001). IL-6 was significantly higher in pSS patients with a positive salivary gland biopsy (P = .04), whole stimulated saliva hyposalivation (P = .02), and presence of musculoskeletal disorders (P = .03). There was a non-significant positive correlation between IL-6 levels and PROMs for xerostomia (r = .31; P = .06) and OHIP-14 (r = .07; P = .68) in pSS patients. Levels of IL-4 and IL-5 were not detected in both pSS and HCs patients.

CONCLUSIONS

Salivary IL-6 levels are significantly associated with pSS patients, and therefore, it is hypothesized that this biomarker may be useful in the diagnosis and follow-up of this disease.

Pathophysiology of IgG4-related disease: A T follicular helper cells disease?

IgG4-related disease is a chronic inflammatory disease characterized by clinical, biological and pathological unifying findings. Because these criteria are not always all together available in patients and because biological and pathological markers are not totally specific, the diagnosis should be retained after exclusion of mimickers. Since the individualization of IgG4-RD, several studies have allowed to better characterize immunological abnormalities associated with this particular condition. B and T cell oligoclonal activation is associated with T helper 2 cytokine production leading to IgG4 production and profibrotic cytokine release. A central role for T follicular helper 2 cells is suggested from recent findings. We summarize here recent advances in understanding of immune abnormalities in IgG4-related disease.

Immunological mechanism of IgG4-related disease

IgG4-related disease (IgG4-RD) is an immune-mediated inflammatory disorder in multiple organs, characterized by abundant infiltration of IgG4-positive plasmacytes and fibrosis in the involved organs. The precise pathogenic mechanism of IgG4-RD still remains unclear. Aberrant innate and adaptive immunity are considered as the main pathogenesis of IgG4-RD. Recent studies have shown that abnormal adaptive immune responses mediated by T helper type 2 ​cells, regulatory T lymphocytes, CD4+ cytotoxic T lymphocytes, T follicular helper cells, T follicular regulatory cells, PD-1hiCXCR5-peripheral T helper cells and B cell subsets are involved in IgG4-RD. In addition to adaptive immune responses, innate immune responses play pathogenic roles in IgG4-RD. Macrophages, mast cells, basophils, complement, and plasmacytoid dendritic cells are activated to produce various kinds of cytokines in IgG4-RD. This review aims to summarize the most recent knowledge in the pathogenesis of IgG4-RD.

Regulatory B Cells

B cells are typically characterized by their ability to produce antibodies, function as secondary antigen-present cells, and produce various immunoregulatory cytokines. The regulatory B (Breg)-cell population is now widely accepted as an important modulatory component of the immune system that suppresses inflammation. Recent studies indicate that Breg-cell populations are small under physiological conditions but expand substantially in both human patients and murine models of chronic inflammatory diseases, autoimmune diseases, infection, transplantation, and cancer. Almost all B-cell subsets can be induced to form Breg cells. In addition, there are unique Breg-cell subsets such as B10 and Tim-1⁺ B cells. Immunoregulatory function may be mediated by production of cytokines such as IL-10 and TGF-β and ensuing suppression of T cells, by direct cell-cell interactions, and (or) by altering the immune microenvironment. In this chapter, we describe in detail the discovery of Breg cells, their phenotypes, differentiation, function, contributions to disease, and therapeutic potential.

Pathogenesis of IgG4-related disease. Comparison with Sjögren's syndrome

IgG4-related disease (IgG4-RD) is characterized by lympho-plasmacytic infiltration and fibrosis in multiple organs, accompanied by high serum IgG4 levels. Although both IgG4-RD and Sjögren's syndrome (SS) frequently affect salivary and lacrimal glands, the clinical and pathological features of these two conditions are different. In an attempt to delineate the pathomechanisms of IgG4-RD, we compared the gene expression patterns of various molecules in labial salivary glands (LSGs) between IgG4-RD and SS. First, using quantitative PCR, we demonstrated significantly higher mRNA expression levels of activation-induced cytidine deaminase (AID), IL-10, and TGFβ in LSGs of IgG4-RD than SS and healthy controls (HCs). We propose that the combination of AID and IL-10 contributes to IgG4-specific immunoglobulin class switch recombination, and that TGFβ induces LSGs fibrosis in IgG4-RD. Second, DNA microarray identified 2641 differentially expressed genes (DEGs) in LSGs; with 1321 up-regulated and 1320 down-regulated genes in IgG4-RD, relative to SS. Among the up-regulated DEGs in IgG4-RD, quantitative PCR confirmed significantly higher expression levels of chemokine (C-C motif) ligand 18 (CCL18) and lactotransferrin in LSGs of IgG4-RD than SS and HCs. The former has chemotactic activity on various types of lymphocytes and enhances collagen production from fibroblasts, while lactotransferrin is an iron-binding protein abundantly present in milk and has a wide range of functions, including fibroblast proliferation and maturation of dendritic cells (DCs). Third, immunofluorescence staining confirmed specific upregulation of CCL18 in macrophages, CD11c + and B cells, and plasmacytes of LSGs-IgG4-RD. These pathological findings could help in the identification of disease-specific biomarkers as well as development of novel therapeutic strategies.

Regulatory B cells: New players in inflammatory and autoimmune rheumatic diseases

OBJECTIVE

Regulatory B cells (Bregs) are a new subset of B cells with immunoregulatory functions, mainly through IL-10 production. Bregs suppress inflammatory Th1 and Th17 differentiation and induce Tregs suppressing autoimmune diseases. The aim of the study was to review the literature related to Bregs in autoimmune rheumatic diseases (ARDs).

METHODS

A literature review of publications in PUBMED published in English was performed using the relevant combinations of terms.

RESULTS

All relevant publications are discussed. Overall, recent studies in rheumatic diseases found Bregs to be decreased in ANCA-associated vasculitides (AAV) and in systemic sclerosis (SSc), particularly in SSc-associated lung fibrosis. In AAV Bregs levels are negatively correlated with autoantibody levels whereas in SSc this association is less clear but there is an inverse association with Th1 and Th17 cells. In rheumatoid arthritis (RA), Bregs were decreased, particularly in RA-associated lung fibrosis. In psoriatic arthritis IL-10 + Bregs are decreased and inversely associated with Th1 and Th17 cells. In systemic lupus erythematosus (SLE), the role of Bregs is unclear. In experimental diseases, when Bregs were expanded ex-vivo, they ameliorated established disease.

CONCLUSION

Bregs appear to be a new player in the pathogenesis of ARDs, and may offer a new strategy for therapeutic intervention.

Defective Regulatory B Cells Are Associated with Thyroid Associated Ophthalmopathy

PURPOSE

To investigate the change of IL-10 producing regulatory B cells (Bregs), which function to suppress peripheral immune responses, in patients with thyroid associated ophthalmopathy (TAO).

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from healthy controls (N=54), patients with Grave's disease (N=26), and TAO patients (N=125), and stimulated with CpG/CD40L. The frequency of IL-10 producing Bregs and the expression of IL-10 in response to thyroid-stimulating hormone (TSH) stimulation were measured by flow cytometry. CD4+ T cells were cultured with Breg-depleted PBMCs to elucidate the function of Bregs in TAO patients. The potential immunoregulatory mechanism was also investigated by western blot and chromatin immunoprecipitation assays.

RESULTS

Active TAO patients had higher baseline levels of Bregs in their peripheral blood than both healthy controls and inactive patients. TSH promoted Bregs. Bregs from TAO patients were defective in suppressing the activation of IFN-γ+ and IL-17+ T cells in vitro.

CONCLUSIONS

We found that regulatory B cells in TAO patients are functionally defective, suggesting the defective Bregs might be responsible for the pathogenesis of TAO.

Aberrant IL-35 levels in patients with primary Sjogren's syndrome

OBJECTIVE

IL-35 is a newly discovered immunoregulatory cytokine that possesses the ability to inhibit CD4 + effector T cells and alleviate autoimmune diseases. The objective of this study was to investigate IL-35 levels in patients with primary Sjogren's syndrome (pSS) and explore the roles of IL-35 in the pathogenesis of pSS.

METHODS

Thirty-four hospitalized patients with pSS were recruited, and 34 volunteers were enrolled as healthy controls. An ELISA was adopted to measure plasma IL-35 levels. The levels of P35 and EBI3 mRNAs in peripheral blood mononuclear cells (PBMCs) were determined using real-time quantitative PCR. The percentage of CD4 + EBI3 + T cells and CD19 + EBI3 + B cells was analysed using flow cytometry. Correlations between IL-35 levels, P35 and EBI3 mRNAs, numbers of CD4 + EBI3 + T cells, CD19 + EBI3 + B cells and clinical parameters were analysed.

RESULTS

Significantly lower plasma IL-35 levels, P35 and EBI3 mRNA levels, and percentages of CD4 + EBI3 + T cells but increased percentages of CD19 + EBI3 + B cells were observed in patients with pSS than in healthy controls. IL-35 levels, EBI3 mRNA expression and the percentage of CD4 + EBI3 + T cells exhibited negative correlations with the ESSDAI score, whereas levels of the IL-35 protein and EBI3 mRNA were negatively correlated with the ESR. Patients who were positive for anti-SSB antibodies presented with lower IL-35 levels and percentages of CD4 + EBI3 + T cells.

CONCLUSIONS

Based on these results, a decrease in the IL-35 levels may play an important role in the pathogenesis of pSS. IL-35 may act as a potential therapeutic agent against inflammation in patients with pSS.

Aberrant Expansion and Function of Follicular Helper T Cell Subsets in IgG4-Related Disease

Objective

To determine the number and function of follicular helper T (Tfh) cell subsets in IgG4‐related disease (IgG4‐RD).

Methods

Mononuclear cells from the peripheral blood and involved tissue of patients with IgG4‐RD were assessed for Tfh cells and their subsets, and levels of B cell lymphoma 6 (Bcl‐6), B lymphocyte–induced maturation protein 1 (BLIMP‐1), and interleukin‐21 (IL‐21) messenger RNA (mRNA). Immunohistochemical and immunofluorescence techniques were used to assess the involved tissue of patients to determine the location of IL‐21, Bcl‐6, and CD4+CXCR5+ Tfh cells. Furthermore, the ability of circulating Tfh (cTfh) cell subsets to induce B cell proliferation, apoptosis, and differentiation and to produce IgG4 was explored in cell cocultures in vitro.

Results

Frequencies of cTfh cells were significantly increased in the peripheral blood of patients with IgG4‐RD, and even higher frequencies were observed in the involved tissue. Percentages of programmed cell death protein 1 in CD4+CXCR5+ICOS+ cTfh cells were positively correlated with the serum levels of IgG and IgG4, IgG4:IgG ratio, number of involved organs, and frequency of CD19+CD24−CD38^high plasmablasts/plasma cells. Levels of BLIMP‐1 and IL‐21 mRNA in peripheral CD4+ T cells were increased in patients with IgG4‐RD compared to healthy controls, and this was correlated with the levels of serum IgG4. Moreover, in the involved tissue, Bcl‐6, IL‐21, and Tfh cells were highly expressed. Compared to cTfh cells from healthy controls, cTfh cells from patients with IgG4‐RD could facilitate B cell proliferation and inhibit B cell apoptosis more efficiently, and enhanced the differentiation of naive B cells into switched memory B cells and plasmablasts/plasma cells, with a resultant increase in the secretion of IgG4. Notably, the cTfh1 and cTfh2 cell subsets were the most effective at providing B cell help.

Conclusion

Tfh cell subsets are expanded in IgG4‐RD and may play pivotal roles in the pathogenesis of the disease.

The Immunologic Paradoxes of IgG4-Related Disease

IgG4-related disease (IgG4-RD), which usually occurs in middle-aged and elderly men, is a newly recognized fibroinflammatory condition characterized by swelling and sclerosis of involved organs, increased IgG4-positive plasma cell infiltration in lesions, and elevated IgG4 concentration in serum. Despite growing interest in the research, the pathophysiological mechanism remains elusive. Most IgG4-RD patients respond well to steroid therapy initially, but recurrent and refractory cases are common, especially in advanced fibrotic stage. Recent studies have documented the heterogeneity of the B cell lineages, which suggests their multiple functions in IgG4-RD beyond IgG4 production, such as cytokine secretion, antigen presentation, autoantibody production, and modulation of T and B cell interactions. Thus, a critical balance exists between pathogenic and regulatory B subsets to prevent immunopathology. A prompt response to B cell depletion therapy reported in recent cases strongly suggests the imbalance within B cell lineages in IgG4-RD. A more precise understanding of the pathogenesis of IgG4-RD will open up new perspectives for therapeutic strategy. With a particular emphasis on the novel B cell-targeted therapeutic strategies, this review highlights the immunologic features of IgG4-RD and the possible roles of B cell lineages in the pathogenesis of IgG4-RD.

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.

Correlation of T follicular helper cells and plasmablasts with the development of organ involvement in patients with IgG4-related disease

Objective

To assess the role of an abnormal immune network in the pathology of IgG4-related disease (IgG4-RD).

Methods

Sixteen patients diagnosed with IgG4-RD at our institution were selected. Peripheral immunocompetent cells were immunophenotyped by multicolour flow cytometry to assess the association between clinical manifestation and pathological findings.

Results

Compared with healthy controls, IgG4-RD patients showed comparable proportions of Th1 and Th17 cells, but higher proportions of Treg and follicular helper T (Tfh) cells. Further, the proportions of class-switched memory B cells and plasmablasts were higher in patients. Among all phenotypes, in particular, the plasmablast proportion increased from 4.2% (controls) to 16.5% (patients). The serum IgG levels were found to be correlated with the proportions of plasmablasts and Tfh cells, but not with those of other T cell subsets. In patients with extraglandular symptoms, only plasmablasts, Tfh cells and memory Treg cells were increased. Histopathological examination revealed a marked Tfh (CD4+ Bcl6+) cell infiltration; the increase of Tfh cells in the peripheral blood thus reflected the degree of Tfh cell infiltration into the tissue. Although steroid therapy reduced plasmablast and Tfh cell proportions, the memory Treg cell proportion remained unchanged.

Conclusion

The association found between Tfh cells and plasmablasts, linked with biological plausibility, suggests that Tfh cells contribute to the pathogenesis of IgG4-RD. Our results also suggested that controlling the Tfh cell-plasmablast axis could be a novel therapeutic strategy for treating IgG4-RD.

Analysis of cell surface and intranuclear markers on non-stimulated human PBMC using mass cytometry

Mass cytometry is a powerful tool that allows simultaneous analysis of more than 37 markers at the single cell level. Mass cytometry is of particular interest in the identification of a wide variety of cell phenotypes in autoimmune diseases. Moreover, cells can be labelled with palladium isotopes and pooled before staining (barcoding). Nevertheless, immunologists often face an important problem concerning the choice of markers to be included in a panel. This problem arises due to the incompatibility of different buffers used for the fixation and permeabilization of cells with various cell surface epitopes. In this study, we used a panel of 27 markers (19 surface markers and 8 intranuclear markers) to demonstrate disparities in the detection of cell surface antigens when comparing different buffers to stain unstimulated peripheral blood mononuclear cells. These disparities range from mild differences to very important differences in population frequencies depending on the buffers. Finally, we demonstrate the harmful effects of permeabilization prior to barcoding on the detection of some cell surface antigens. Here, we optimize a protocol that is suitable to use when targeting a large panel including both cell surface and intranuclear markers on unstimulated human peripheral blood mononuclear cells.

Positive and negative functions of B lymphocytes in tumors

Accumulating evidence indicated that B lymphocytes exerted complex functions in tumor immunity. On the one hand, B lymphocytes can inhibit tumor development through antibody generation, antigen presentation, tumor tissue interaction, and direct killing. On the other hand, B lymphocytes have tumor-promoting functions. A typical type of B lymphocytes, termed regulatory B cells, is confirmed to attenuate immune response in a tumor environment. In this paper, we summarize the current understanding of B-cell functions in tumor immunology, which may shed light on potential therapeutic strategies against cancer.

Role of Microbiota in Strengthening Ocular Mucosal Barrier Function Through Secretory IgA

Purpose

The purpose of this study was to evaluate mechanisms controlling secretory IgA (SIgA) production, thereby ensuring maintenance of ocular surface health.

Methods

To determine whether the presence of specific gut commensal species regulates SIgA levels and IgA transcripts in the eye-associated lymphoid tissues (EALT), specific-pathogen-free (SPF) Swiss Webster (SW) mice were treated with antibiotic cocktails, germ-free (GF) SW mice were reconstituted with diverse commensal gut microbiota, or monocolonized with gut-specific commensals. Proteomic profiling and quantitative real-time polymerase chain reaction (qRT-PCR) were used to quantify SIgA and IgA levels. 16S rDNA sequencing was carried out to characterize commensal microbiota.

Results

Commensal presence regulated ocular surface SIgA levels and mRNA IgA transcripts in EALT. Oral antibiotic cocktail intake significantly reduced gut commensal presence, while maintaining ocular surface commensal levels reduced SIgA and IgA transcripts in EALT. Analysis of gut microbial communities revealed that SPF SW mice carried abundant Bacteroides organisms when compared to SPF C57BL6/N mice, with B. acidifaciens being the most prominent species in SPF SW mice. Monocolonization of GF SW mice with B. acidifaciens, a strict gut anaerobe, resulted in significant increase of IgA transcripts in the EALT, implying generation of B-cell memory.

Conclusions

These data illustrated a “gut-eye” axis of immune regulation. Exposure of the host to gut commensal species may serve as a priming signal to generate B-cell repertoires at sites different from the gut, such as EALT, thereby ensuring broad protection.

Expression of CD markers' in immune thrombocytopenic purpura: prognostic approaches

Immune Thrombocytopenic Purpura (ITP) is a common autoimmune bleeding disorder characterized by a reduction in peripheral blood platelet counts. In this disease, autoantibodies (Auto-Abs) are produced against platelet GPIIb/GPIIIa by B cells, which require interaction with T cells. In this review, the importance of B and T lymphocytes in ITP prognosis has been studied. Relevant literature was identified by a PubMed search (1990-2016) of English-language papers using the terms B and T lymphocyte, platelet, CD markers and immune thrombocytopenic purpura. T and B lymphocytes are the main immune cells in the body. Defective function causes disrupted balance of different subgroups of lymphocytes, and abnormal expression of surface markers of these cells results in self-tolerance dysfunction, as well as induction of Auto-Abs against platelet glycoproteins (PG). Given the role of B and T cells in production of autoantibodies against PG, it can be stated that the detection of changes in CD markers' expression in these cells can be a good approach for assessing prognosis in ITP patients.