Both Treg cells and Tconv cells are defective in the Myasthenia gravis thymus: roles of IL-17 and TNF-α

Spatial transcriptomics elucidates medulla niche supporting germinal center response in myasthenia gravis-associated thymoma

Myasthenia gravis (MG) is etiologically associated with thymus abnormalities, but its pathology in the thymus remains unclear. In this study, we attempt to narrow down the features associated with MG using spatial transcriptome analysis of thymoma and thymic hyperplasia samples. We find that the majority of thymomas are constituted by the cortical region. However, the small medullary region is enlarged in seropositive thymomas and contains polygenic enrichment and MG-specific germinal center structures. Neuromuscular medullary thymic epithelial cells, previously identified as MG-specific autoantigen-producing cells, are enriched in the cortico-medullary junction. The medulla is characterized by a specific chemokine pattern and immune cell composition, including migratory dendritic cells and effector regulatory T cells. Similar germinal center structures and immune microenvironments are also observed in the thymic hyperplasia medulla. This study shows that the medulla and junction areas are linked to MG pathology and provides insights into future MG research.

Non-Coding RNAs in Myasthenia Gravis: From Immune Regulation to Personalized Medicine

Myasthenia gravis (MG) is an antibody-mediated autoimmune disorder characterized by altered neuromuscular transmission, which causes weakness and fatigability in the skeletal muscles. The etiology of MG is complex, being associated with multiple genetic and environmental factors. Over recent years, progress has been made in understanding the immunological alterations implicated in the disease, but the exact pathogenesis still needs to be elucidated. A pathogenic interplay between innate immunity and autoimmunity contributes to the intra-thymic MG development. Epigenetic changes are critically involved in both innate and adaptive immune response regulation. They can act as (i) pathological factors besides genetic predisposition and (ii) co-factors contributing to disease phenotypes or patient-specific disease course/outcomes. This article reviews the role of non-coding RNAs (ncRNAs) as epigenetic factors implicated in MG. Particular attention is dedicated to microRNAs (miRNAs), whose expression is altered in MG patients' thymuses and circulating blood. The long ncRNA (lncRNA) contribution to MG, although not fully characterized yet, is also discussed. By summarizing the most recent and fast-growing findings on ncRNAs in MG, we highlight the therapeutic potential of these molecules for achieving immune regulation and their value as biomarkers for the development of personalized medicine approaches to improve disease care.

Non-coding RNA and its network in the pathogenesis of Myasthenia Gravis

Myasthenia Gravis (MG) is a chronic autoimmune disease that primarily affects the neuromuscular junction, leading to muscle weakness in patients with this condition. Previous studies have identified several dysfunctions in thymus and peripheral blood mononuclear cells (PBMCs), such as the formation of ectopic germinal centers in the thymus and an imbalance of peripheral T helper cells and regulatory T cells, that contribute to the initiation and development of MG. Recent evidences suggest that noncoding RNA, including miRNA, lncRNA and circRNA may play a significant role in MG progression. Additionally, the network between these noncoding RNAs, such as the competing endogenous RNA regulatory network, has been found to be involved in MG progression. In this review, we summarized the roles of miRNA, lncRNA, and circRNA, highlighted their potential application as biomarkers in diagnosing MG, and discussed their potential regulatory networks in the abnormal thymus and PBMCs during MG development.

Thymic gene expression analysis reveals a potential link between HIF-1A and Th17/Treg imbalance in thymoma associated myasthenia gravis

Myasthenia gravis (MG) is an immune-mediated disease frequently associated with thymic changes. Increased T helper 17 (Th17) cell activity and dysfunctional regulatory T (Treg) cells have been demonstrated in subgroups of MG. On the other hand, hypoxia-inducible factor 1 (HIF-1) has been shown to regulate the Th17/Treg balance by inducing Th17 differentiation while attenuating Treg development. To identify the underlying mechanisms of different thymic pathologies in MG development, we evaluated thymic samples from thymoma-associated myasthenia gravis (TAMG), MG with hyperplasia (TFH-MG) and thymoma without MG (TOMA) patients. Differential gene expression analysis revealed that TAMG and TFH-MG cells are associated with different functional pathways. A higher RORC/FOXP3 ratio provided evidence for Th17/Treg imbalance in TAMG potentially related to increased HIF1A. The hypoxic microenvironment in thymoma may be a driver of TAMG by increasing HIF1A. These findings may lead to new therapeutic approaches targeting HIF1A in the development of TAMG.

Autoimmune and Non-Autoimmune Comorbidities in Myasthenic Patients of East-European Descent: A Case-Control Study

Background: As the life expectancy of patients with myasthenia gravis (MG) is improving, so the number of comorbidities continues to rise, with a potentially significant impact on the overall morbidity and mortality. The main aim of the study was to assess comorbidities of MG in a group of patients of East-European descent. Methods: We retrospectively compared 185 adult myasthenic patients with 895 sex- and age-matched controls, admitted from January 2013 to December 2021. Results: Of these patients, 60% had late-onset MG (LOMG), with a clear predominance of women in both the LOMG and early-onset (EOMG) types; and 23.8% of the patients had a radiological description consistent with thymoma. All myasthenic patients had at least one comorbidity; 20 (10.8%) of the patients associated at least one autoimmune comorbidity. Obesity (p < 0.01), type 2 diabetes (p < 0.0001), cerebrovascular diseases (p < 0.0001), essential hypertension (p < 0.01), and cardiac arrythmias (p < 0.0001) were more frequent in patients than in the control group. The granulocyte-to-lymphocyte ratio was higher in the myasthenic patients compared to the controls (p < 0.01 for LOMG). Discussion: We, thus, suggest a common chronic low-grade inflammatory background as a possible connection between MG subtypes and some of these apparently unconnected comorbidities. Conclusions: The East-European origin of the patients offered a different social and cultural angle of a disease studied mainly on populations of West-European and Asian descent.

An integrative mechanistic model of thymocyte dynamics

Background

The thymus plays a central role in shaping human immune function. A mechanistic, quantitative description of immune cell dynamics and thymic output under homeostatic conditions and various patho-physiological scenarios are of particular interest in drug development applications, e.g., in the identification of potential therapeutic targets and selection of lead drug candidates against infectious diseases.

Methods

We here developed an integrative mathematical model of thymocyte dynamics in human. It incorporates mechanistic features of thymocyte homeostasis as well as spatial constraints of the thymus and considerations of age-dependent involution. All model parameter estimates were obtained based on published physiological data of thymocyte dynamics and thymus properties in mouse and human. We performed model sensitivity analyses to reveal potential therapeutic targets through an identification of processes critically affecting thymic function; we further explored differences in thymic function across healthy subjects, multiple sclerosis patients, and patients on fingolimod treatment.

Results

We found thymic function to be most impacted by the egress, proliferation, differentiation and death rates of those thymocytes which are most differentiated. Model predictions also showed that the clinically observed decrease in relapse risk with age, in multiple sclerosis patients who would have discontinued fingolimod therapy, can be explained mechanistically by decreased thymic output with age. Moreover, we quantified the effects of fingolimod treatment duration on thymic output.

Conclusions

In summary, the proposed model accurately describes, in mechanistic terms, thymic output as a function of age. It may be further used to perform predictive simulations of clinically relevant scenarios which combine specific patho-physiological conditions and pharmacological interventions of interest.

MicroRNA‑155‑5p affects regulatory T cell activation and immunosuppressive function by targeting BCL10 in myasthenia gravis

The imbalance in immune homeostasis plays a crucial role in the pathogenesis of myasthenia gravis (MG). MicroRNAs (miRs) have been identified as key regulators of immune homeostasis. B-cell lymphoma/leukemia 10 (BCL10) has been implicated in the activation and suppressive function of regulatory T cells (Tregs). This study aimed to investigate the potential role of miR-155-5p in modulating the activation and function of Tregs in MG. To achieve this objective, blood samples were collected from MG patients to assess the expression levels of miR-155-5p and BCL10, as well as the proportion of circulating Tregs, in comparison to healthy controls. The correlation between miR-155-5p and BCL10 levels was evaluated in human samples. The expression levels of miR-155-5p and the numbers of circulating Tregs were also examined in an animal model of experimental autoimmune MG (EAMG). A dual-luciferase reporter assay was used to verify whether miR-155-5p can target BCL10. To determine the regulatory function of BCL10 in Tregs, CD4+ CD25+ Tregs were transfected with either small interfering-BCL10 or miR-155-5p inhibitor, and the expression levels of the anti-inflammatory cytokine IL-10 and transcription factors Foxp3, TGF-β1, CTLA4, and ICOS were measured. The results demonstrated that the expression level of miR-155-5p was significantly higher in patients with MG compared with that in healthy controls, whereas the expression level of BCL10 was significantly decreased in patients with MG. Furthermore, there was a significant negative correlation between the expression levels of miR-155-5p and BCL10. The number of circulating Tregs was significantly reduced in patients with MG and in the spleen of rats with EAMG compared with that in the corresponding control groups. The dual-luciferase reporter assay demonstrated that miR-155-5p could target BCL10. The Tregs transfected with si-BCL10 demonstrated significant decreases in the protein levels of TGF-β1 and IL-10, as well as in the mRNA expression levels of Foxp3, TGF-β1, CTLA-4 and ICOS. Conversely, the Tregs transfected with the miR-155-5p inhibitor exhibited a substantial increase in these protein and mRNA expression levels compared with their respective control groups. Furthermore, the knockdown of BCL10 exhibited a decline in the suppressive efficacy of Tregs on the proliferation of CD4+ T cells. Conversely, the suppression of miR-155-5p expression attenuated the inhibition of the BCL10 gene, potentially causing an indirect influence on the suppressive capability of Tregs on the proliferation of CD4+ T cells. BCL10 was thus found to contribute to the activation and immunosuppressive function of Tregs. In summary, the present study demonstrated that miR-155-5p inhibited the activation and immunosuppressive function of Tregs by targeting BCL10, which may be used as a future potential target for the treatment of MG.

[Experience of using eculizumab in refractory myasthenia gravis]

Myasthenia gravis (MG) is a chronic autoimmune disease mediated by autoreactive T- and B-cells and manifested by progressive pathological muscle weakness and fatigue. Traditional immunomodulatory treatment does not always lead to the clinical picture significant improvement, despite adequate dosage and duration of use. Refractory myasthenia gravis requires new therapeutic approaches development and implementation. The range of target innovative agents in refractory MG includes monoclonal antibodies, which act directly on individual components of the complement system. Based on the results of randomized controlled trials, data on the effectiveness and safety of eculizumab, which inhibits the C5 component of the complement system, is presented. We present our own clinical experience of using eculizumab in a young woman with refractory generalized AChR-positive MG with a rapid decrease in the severity of symptoms to a minimum level and restoration of ability to work, and the absence of adverse events during therapy.

Regulatory T-cell therapy approaches

Regulatory T cells (Tregs) have enormous therapeutic potential to treat a variety of immunopathologies characterized by aberrant immune activation. Adoptive transfer of ex vivo expanded autologous Tregs continues to progress through mid- to late-phase clinical trials in several disease spaces and has generated promising preliminary safety and efficacy signals to date. However, the practicalities of this strategy outside of the clinical trial setting remain challenging. Here, we review the current landscape of regulatory T-cell therapy, considering emergent approaches and technologies presenting novel ways to engage Tregs, and reflect on the progress necessary to deliver their therapeutic potential to patients.

Blocking interleukin-23 ameliorates neuromuscular and thymic defects in myasthenia gravis

Acetylcholine receptor (AChR) myasthenia gravis (MG) is a chronic autoimmune disease characterized by muscle weakness. The AChR⁺ autoantibodies are produced by B-cells located in thymic ectopic germinal centers (eGC). No therapeutic approach is curative. The inflammatory IL-23/Th17 pathway is activated in the thymus as well as in the blood and the muscle, contributing to the MG pathogenic events. We aimed to study a potential new therapeutic approach that targets IL-23p19 (IL-23) in the two complementary preclinical MG models: the classical experimental MG mouse model (EAMG) based on active immunization and the humanized mouse model featuring human MG thymuses engrafted in NSG mice (NSG-MG). In both preclinical models, the anti-IL-23 treatment ameliorated MG clinical symptoms. In the EAMG, the treatment reduced IL-17 related inflammation, anti-AChR IgG2b antibody production, activated transduction pathway involved in muscle regeneration and ameliorated the signal transduction at the neuromuscular junction. In the NSG-MG model, the treatment reduced pathogenic Th17 cell population and expression of genes involved in eGC stabilization and B-cell development in human MG thymus biopsies. Altogether, these data suggest that a therapy targeting IL-23p19 may promote significant clinical ameliorations in AChR⁺ MG disease due to concomitant beneficial effects on the thymus and skeletal muscle defects.

Expression of TRAF6 in peripheral blood B cells of patients with myasthenia gravis

Background

Tumor necrosis factor receptor-associated factor 6 (TRAF6) can regulate the activation of inflammatory signaling pathways by acting as an E3 ubiquitin ligase, which enhances B cell activation. This study aimed to evaluate the expression of TRAF6 in the peripheral blood B cells of myasthenia gravis (MG) patients and analyze the relationships between TRAF6 expression and clinical characteristics.

Method

In our study, the expression level of TRAF6 in peripheral blood B cells of 89 patients was measured by flow cytometry compared with that of healthy subjects. The effects of disease severity, MG classification and immunotherapy on TRAF6 expression level were also analyzed.

Results

In our study, TRAF6 expression was elevated in CD19⁺ B cells and CD19⁺CD27⁺ memory B cells in generalized MG (GMG) patients compared with ocular MG (OMG) patients (p = 0.03 and p = 0.03, respectively). There was a significant positive correlation between the TRAF6 expression level and disease severity in both OMG patients and GMG patients (CD19⁺ B cells: OMG: p < 0.001, r = 0.89; GMG: p = 0.001, r = 0.59; CD29⁺CD27⁺ B cells: OMG: p = 0.001, r = 0.80; GMG: p = 0.048, r = 0.38). TRAF6 expression was significantly elevated in CD19⁺ B cells and CD19⁺CD27⁺ memory B cells in GMG with acute aggravation compared with GMG in MMS (p = 0.009 and p = 0.028, respectively). In the eleven MG patients who were followed, TRAF6 expression in B cells and memory B cells was significantly decreased after treatment (p = 0.03 and p < 0.01, respectively).

Conclusion

TRAF6 is potentially a useful biomarker of inflammation in patients with MG, and might be used to evaluate the effectiveness of treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02833-9.

Comparison of Peripheral Blood Regulatory T Cells and Functional Subsets Between Ocular and Generalized Myasthenia Gravis

Purpose

This study aims to discuss the function mechanism of regulatory T cells and its subsets in the pathogenic process of myasthenia gravis by contracting the activation levels of those cells in peripheral blood among healthy people, patients with ocular myasthenia gravis (oMG) and patients with generalized myasthenia gravis (gMG).

Method

Healthy people, newly diagnosed oMG patients, and gMG patients were enrolled in this study. The percentage of the CD3⁺CD4⁺CD25⁺ Treg cells, CD3⁺CD4⁺CD25⁺Foxp3⁺ Treg cells, CD3⁺CD4⁺CD25⁺Foxp3^hi CD45RA^–aTreg cells, CD3⁺CD4⁺CD25⁺Foxp3^loCD45RA^–n-sTreg cells, and CD3⁺CD4⁺CD25⁺ Foxp3^loCD45RA⁺rTreg cells in the peripheral blood were examined by flow cytometry. And then analyzed the differences of Treg cells and its subsets among the study members.

Results

The percentage of the CD4⁺CD25⁺Treg cells in the peripheral blood of oMG patients and gMG patients were both lower than that of healthy people (p < 0.05), the percentage of patients with oMG had no distinct difference with that of patients with gMG (p = 0.475), however. Also, the percentage of CD3⁺CD4⁺CD25⁺Foxp3⁺Treg cells in the oMG and gMG patients’ group were both lower than that of healthy group. And the percentage of CD25⁺Foxp3⁺Treg cells in the peripheral blood of patients with oMG and healthy people were both higher than that of patients with gMG (p < 0.05). The percentage of rTreg in the CD3⁺CD4⁺CD25⁺Treg of the peripheral blood for both gMG and oMG patients’ group were lower than healthy group (p < 0.05), but there was no statistical significance between the oMG and gMG patients’ group (p = 0.232). The percentage of the aTreg cells in the CD3⁺CD4⁺CD25⁺Treg cells of the peripheral blood for the oMG patients was higher than that of gMG patients (p < 0.05), but both of them were lower than healthy group (p < 0.05). The percentage of n-sTreg cells in the peripheral blood descended among the gMG patients’ group, oMG patients’ group, and healthy group (p < 0.05).

Conclusion

The changes in the number and function of Treg cells and its subsets can cause the impairment of negative immune regulation, which may mediate the triggering of oMG and its progression to gMG.

Long non-coding RNA growth arrest specific 5 regulates the T helper 17/regulatory T balance by targeting miR-23a in myasthenia gravis

OBJECTIVE

Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disorder. Recent studies report that long non-coding RNAs (lncRNAs) play vital roles in the pathogenesis of various diseases. This study explored the molecular mechanism of lncRNA growth arrest specific 5 (GAS5) in regulating the T helper 17 (Th17)/regulatory T (Treg) cell balance in MG.

METHODS

GAS5 and miR-23a expression levels were detected by quantitative reverse transcription polymerase chain reaction. Flow cytometry was performed to examine the proportion of Th17 and Treg cells in CD4+ T cells from MG patients. The interaction between GAS5 and miR-23a was verified by luciferase reporter and RNA immunoprecipitation assays. Levels of Th17 and Treg-related proteins were examined using western blots and enzyme-linked immunosorbent assays.

RESULTS

GAS5 expression levels were significantly decreased in the CD4+ T cells of MG patients, and GAS5 overexpression restrained Th17 differentiation in CD4+ T cells. Moreover, miR-23a was confirmed as a downstream target of GAS5 and negatively regulated by GAS5 through a direct interaction. Further exploration showed that GAS5 can inhibit Th17 differentiation by downregulating miR-23a.

CONCLUSION

Collectively, our results indicate that GAS5 can regulate the Th17/Treg balance by targeting miR-23a expression, providing a scientific basis for clinical therapeutic development for MG.

Myasthenia Gravis: An Acquired Interferonopathy?

Myasthenia gravis (MG) is a rare autoimmune disease mediated by antibodies against components of the neuromuscular junction, particularly the acetylcholine receptor (AChR). The thymus plays a primary role in AChR-MG patients. In early-onset AChR-MG and thymoma-associated MG, an interferon type I (IFN-I) signature is clearly detected in the thymus. The origin of this chronic IFN-I expression in the thymus is not yet defined. IFN-I subtypes are normally produced in response to viral infection. However, genetic diseases called interferonopathies are associated with an aberrant chronic production of IFN-I defined as sterile inflammation. Some systemic autoimmune diseases also share common features with interferonopathies. This review aims to analyze the pathogenic role of IFN-I in these diseases as compared to AChR-MG in order to determine if AChR-MG could be an acquired interferonopathy.

Antibody Therapies in Autoimmune Neuromuscular Junction Disorders: Approach to Myasthenic Crisis and Chronic Management

Myasthenia gravis (MG) is a neurological autoimmune disorder characterized by muscle weakness and fatigue. It is a B cell-mediated disease caused by pathogenic antibodies directed against various components of the neuromuscular junction (NMJ). Despite the wide range of adverse effects, current treatment is still based on non-specific immunosuppression, particularly on long-term steroid usage. The increasing knowledge regarding the pathogenic mechanisms of MG has however allowed to create more target-specific therapies. A very attractive therapeutic approach is currently offered by monoclonal antibodies (mAbs), given their ability to specifically and effectively target different immunopathological pathways, such as the complement cascade, B cell-related cluster of differentiation (CD) proteins, and the human neonatal Fc receptor (FcRn). Up to now, eculizumab, a C5-directed mAb, has been approved for the treatment of generalized MG (gMG) and efgartigimod, a FcRn inhibitor, has just been approved by the U.S. Food and Drug Administration for the treatment of anti-acetylcholine receptor (AChR) antibody positive gMG. Other mAbs are currently under investigation with encouraging preliminary results, further enriching the new range of therapeutic possibilities for MG. This review article provides an overview of the present status of mAb-based therapies for MG, which offer an exciting promise for better outcomes by setting the basis of a precision medicine approach.

Lymphocyte activation gene-3 (LAG-3) regulatory T cells: An evolving biomarker for treatment response in autoimmune diseases

Regulatory T cells (Tregs) comprise a CD4⁺CD25⁺Foxp3⁺ T cell subset for maintaining immune tolerance, and their deficits and/or dysfunction are observed in autoimmune diseases. The lymphocyte activation gene 3 (LAG-3, also known as CD223), which is an immunoglobulin superfamily member expressed on peripheral immune cells, is recognized as an inhibitory regulator of Tregs. LAG-3⁺ T cells represent a novel protective Tregs subset that produces interleukin-10. Alterations in LAG-3⁺ Tregs have been reported in several autoimmune diseases, suggesting their potential pathogenic role. Recent studies have indicated that LAG-3⁺ Tregs may be associated not only with immunopathology but also with response to therapy in several autoimmune and autoinflammatory diseases, such as rheumatoid arthritis, psoriasis, psoriatic arthritis and others. We present a review of Tregs phenotypes and functions, with a focus on LAG-3⁺ Tregs, and discuss their potential role as biomarkers for treatment response in autoimmune diseases.

Herpesvirus entry mediator on T cells as a protective factor for myasthenia gravis: A Mendelian randomization study

Background and objectives

Myasthenia gravis (MG) is a T cell-driven, autoantibody-mediated disorder affecting transmission in neuromuscular junctions. The associations between the peripheral T cells and MG have been extensively studied. However, they are mainly of observational nature, thus limiting our understanding of the effect of inflammatory biomarkers on MG risk. With large data sets now available, we used Mendelian randomization (MR) analysis to investigate whether the biomarkers on T cells are causally associated with MG and further validate the relationships.

Methods

We performed a two-sample MR analysis using genetic data from one genome-wide association study (GWAS) for 210 extensive T-cell traits in 3,757 general population individuals and the largest GWAS for MG currently available (1,873 patients versus 36,370 age/gender-matched controls) from US and Italy. Then the biomarkers of interest were validated separately in two GWASs for MG in FIN biobank (232 patients versus 217,056 controls) and UK biobank (152 patients versus 386,631 controls).

Results

In the first analysis, three T-cell traits were identified to be causally protective for MG risk: 1) CD8 on terminally differentiated CD8⁺ T cells (OR [95% CI] = 0.71 [0.59, 0.86], P = 5.62e-04, adjusted P =2.81e-02); 2) CD4⁺ regulatory T proportion in T cells (OR [95% CI] = 0.44 [0.26, 0.72], P = 1.30e-03, adjusted P =2.81e-02); 3) HVEM expression on total T cells (OR [95% CI] = 0.67 [0.52, 0.86], P = 1.61e-03, adjusted P =2.81e-02) and other eight T-cell subtypes (e.g., naïve CD4+ T cells). In particular, HVEM is a novel immune checkpoint on T cells that has never been linked to MG before. The SNPs on the TNFRSF14 per se further support a more direct link between the HVEM and MG. The validation analysis replicated these results in both FIN and UK biobanks. Both datasets showed a concordant protective trend supporting the findings, albeit not significant.

Conclusion

This study highlighted the role of HVEM on T cells as a novel molecular-modified factor for MG risk and validated the causality between T cells and MG. These findings may advance our understanding of MG's immunopathology and facilitate the future development of predictive disease-relevant biomarkers.

Epstein-Barr Virus in Myasthenia Gravis: Key Contributing Factor Linking Innate Immunity with B-Cell-Mediated Autoimmunity

Epstein-Barr virus (EBV), a common human herpes virus latently infecting most of the world’s population with periodic reactivations, is the main environmental factor suspected to trigger and/or sustain autoimmunity by its ability to disrupt B-cell tolerance checkpoints. Myasthenia gravis (MG) is a prototypic autoimmune disorder, mostly caused by autoantibodies to acetylcholine receptor (AChR) of the neuromuscular junction, which cause muscle weakness and fatigability. Most patients display hyperplastic thymus, characterized by ectopic germinal center formation, chronic inflammation, exacerbated Toll-like receptor activation, and abnormal B-cell activation. After an overview on MG clinical features and intra-thymic pathogenesis, in the present chapter, we describe our main findings on EBV presence in MG thymuses, including hyperplastic and thymoma thymuses, in relationship with innate immunity activation and data from other autoimmune conditions. Our overall data strongly indicate a critical contribution of EBV to innate immune dysregulation and sustained B-cell-mediated autoimmune response in the pathological thymus of MG patients.

Roles of IL-35-producing T and B cells in anti-acetylcholine receptor antibody-positive myasthenia gravis

BACKGROUND

Interleukin 35 (IL-35) plays an anti-inflammatory in numerous autoimmune diseases. However, the potential roles of IL-35-producing T and B cells and serum IL-35 levels in the pathogenesis of myasthenia gravis (MG) and its association with disease activity in patients with MG remain unclear.

METHODS

The percentages of IL-35-producing CD4 + CD25 + T cells and CD19 + B cells among peripheral blood mononuclear cells were determined in 37 patients with anti-acetylcholine receptor (AChR) antibody-positive MG and 35 healthy controls (HCs) by performing a flow cytometry analysis. Serum IL-35 levels in participants were determined using an enzyme-linked immunosorbent assay. Further, the correlations between IL35 levels and disease activity were analysed.

RESULTS

The percentages of IL-35-producing CD4 + CD25 + T cells and CD19 + B cells were significantly lower in patients with anti-AChR antibody-positive MG than in HCs (p = 0.001 and p = 0.002, respectively). Furthermore, patients with thymoma and patients with generalized MG had lower percentages of IL-35-producing CD4 + CD25 + T cells and CD19 + B cells than those without thymoma and those with ocular MG (p = 0.001 and p = 0.003; p = 0.008 and p = 0.001, respectively). Interestingly, the suppression of IL-35 secretion correlated negatively with the activities of daily living scores of patients with MG (r = -0.4774, p = 0.0028) and the quantitative MG scores (r = -0.4656, p = 0.0037). The proportions of IL-35-producing T cells and B cells and serum levels of IL-35 increased after treatment.

CONCLUSIONS

IL-35 may represent a potential biomarker for the clinical evaluation of MG.

Absence of Association between Previous Mycoplasma pneumoniae Infection and Subsequent Myasthenia Gravis: A Nationwide Population-Based Matched Cohort Study

Mycoplasma pneumoniae (M. pneumoniae) is not only one of the most common pathogenic bacteria for respiratory infection but also a trigger for many autoimmune diseases. Its infection process shared many similarities with the pathogenesis of myasthenia gravis (MG) at cellular and cytokine levels. Recent case reports demonstrated patients present with MG after M. pneumoniae infection. However, no epidemiological studies ever looked into the association between the two. Our study aimed to investigate the relationship between M. pneumoniae infection and subsequent development of MG. In this population-based retrospective cohort study, the risk of MG was analyzed in patients who were newly diagnosed with M. pneumoniae infection between 2000 and 2013. A total of 2428 M. pneumoniae patients were included and matched with the non-M. pneumoniae control cohort at a 1:4 ratio by age, sex, and index date. Cox proportional hazards regression analysis was applied to analyze the risk of MG development after adjusting for sex, age, and comorbidities, with hazard ratios and 95% confidence intervals. The incidence rates of MG in the non-M. pneumoniae and M. pneumoniae cohorts were 0.96 and 1.97 per 10,000 person-years, respectively. Another case-control study of patients with MG (n = 515) was conducted to analyze the impact of M. pneumoniae on MG occurrence as a sensitivity analysis. The analysis yielded consistent absence of a link between M. pneumoniae and MG. Although previous studies have reported that M. pneumoniae infection and MG may share associated immunologic pathways, we found no statistical significance between M. pneumoniae infection and subsequent development of MG in this study.

Single-cell profiling of myasthenia gravis identifies a pathogenic T cell signature

Myasthenia gravis (MG) is an autoimmune disease characterized by impaired neuromuscular signaling due to autoantibodies targeting the acetylcholine receptor. Although its auto-antigens and effector mechanisms are well defined, the cellular and molecular drivers underpinning MG remain elusive. Here, we employed high-dimensional single-cell mass and spectral cytometry of blood and thymus samples from MG patients in combination with supervised and unsupervised machine-learning tools to gain insight into the immune dysregulation underlying MG. By creating a comprehensive immune map, we identified two dysregulated subsets of inflammatory circulating memory T helper (Th) cells. These signature Th_CD103 and Th_GM cells populated the diseased thymus, were reduced in the blood of MG patients, and were inversely correlated with disease severity. Both signature Th subsets rebounded in the blood of MG patients after surgical thymus removal, indicative of their role as cellular markers of disease activity. Together, this in-depth analysis of the immune landscape of MG provides valuable insight into disease pathogenesis, suggests novel biomarkers and identifies new potential therapeutic targets for treatment.

Myasthenia Gravis: Epidemiology, Pathophysiology and Clinical Manifestations

Myasthenia gravis (MG) is an autoimmune neurological disorder characterized by defective transmission at the neuromuscular junction. The incidence of the disease is 4.1 to 30 cases per million person-years, and the prevalence rate ranges from 150 to 200 cases per million. MG is considered a classic example of antibody-mediated autoimmune disease. Most patients with MG have autoantibodies against the acetylcholine receptors (AChRs). Less commonly identified autoantibodies include those targeted to muscle-specific kinase (MuSK), low-density lipoprotein receptor-related protein 4 (Lrp4), and agrin. These autoantibodies disrupt cholinergic transmission between nerve terminals and muscle fibers by causing downregulation, destruction, functional blocking of AChRs, or disrupting the clustering of AChRs in the postsynaptic membrane. The core clinical manifestation of MG is fatigable muscle weakness, which may affect ocular, bulbar, respiratory and limb muscles. Clinical manifestations vary according to the type of autoantibody, and whether a thymoma is present.

SS-A52 antigen expression in thymic carcinoma accompanied with Sjögren syndrome: A case report

RATIONALE

The relationship between thymic tumors and Sjögren syndrome (SjS) is unknown, and surgical resection has not been optimized. Especially, thymic carcinoma with autoimmune disease is rare. Analysis of SS-A52, germinal centers, plasma cells, and Foxp3+ Treg in thymic carcinoma has never been reported, and their pathological roles in causing SjS have not been studied.

PATIENT CONCERNS

A 78-year-old man presented with sputum production and xerostomia while asleep. Chest computed tomography showed a homogeneous and hypodense mass in the anterosuperior mediastinum. Serum levels of the antinuclear antibody, antibody to SS-A, and antibody to SS-B were positive.

DIAGNOSES

Thymic carcinoma (squamous cell carcinoma) and SjS.

INTERVENTIONS

Video-assisted thoracoscopic resection of the mediastinal tumor and postoperative radiation therapy was performed.

OUTCOMES

The histological diagnosis was thymic squamous cell carcinoma. Histologically, the squamous carcinomatous cells were arranged in nests and cords in the fibrohyaline stroma with capsular invasion. In the stroma, dense lymphoid tissues containing large reactive germinal centers and many plasma cells were also noted. In the involuted thymus, CD20-positive mature lymphocytes infiltrated, and germinal centers were noted. Double immunohistochemical staining revealed that SS-A52 antigen was positive in both the carcinoma component and CD20-positive mature B cells. Postoperatively, the xerostomia persisted, and serum SS-A and SS-B remained positive. No evidence of carcinoma recurrence with chest computed tomography scan was observed at 18-months follow-up.

LESSONS

In the surgical treatment of thymic tumors with SjS, extended thymectomy might be worth considering to stop the progressive destruction of the targets of SjS-specific autoantibodies. However, the postoperative symptoms may not dramatically improve because the target organs might have changed irreversibly, and memory B cells might persist. This is the first report that demonstrated the SS-A52 antigen presentation in a thymic tumor to the best of our knowledge.

Modulation of immune responses by bile acid receptor agonists in myasthenia gravis

Bile acids bind to multiple receptors, including Takeda G protein-coupled receptor 5 (TGR5) and farnesoid-X-receptors alpha (FXRα). We compared the response of PBMCs to the activation of these receptors in healthy controls and myasthenic patients. We found that TGR5 is a more potent negative regulator of T cell cytokine response than FXRα in both groups. In contrast, TGR5 and FXRα agonists elicit distinct B cell responses in myasthenia compared to controls, specifically on the frequency of IL-6⁺ B cells and regulatory B cells, as well as IL-10 secretion from PBMCs. We propose that TGR5 is a potential therapeutic target in myasthenia.

Immunoregulatory Cells in Myasthenia Gravis

Myasthenia gravis (MG) is a T cell-dependent, B-cell mediated autoimmune disease caused by antibodies against the nicotinic acetylcholine receptor or other components of the post-synaptic muscle endplate at the neuromuscular junction. These specific antibodies serve as excellent biomarkers for diagnosis, but do not adequately substitute for clinical evaluations to predict disease severity or treatment response. Several immunoregulatory cell populations are implicated in the pathogenesis of MG. The immunophenotype of these populations has been well-characterized in human peripheral blood. CD4⁺FoxP3⁺ regulatory T cells (Tregs) are functionally defective in MG, but there is a lack of consensus on whether they show numerical perturbations. Myeloid-derived suppressor cells (MDSCs) have also been explored in the context of MG. Adoptive transfer of CD4⁺FoxP3⁺ Tregs or MDSCs suppresses ongoing experimental autoimmune MG (EAMG), a rodent model of MG, suggesting a protective role of both populations in this disease. An imbalance between follicular Tregs and follicular T helper cells is found in untreated MG patients, correlating with disease manifestations. There is an inverse correlation between the frequency of circulating IL-10–producing B cells and clinical status in MG patients. Taken together, both functional and numerical defects in various populations of immunoregulatory cells in EAMG and human MG have been demonstrated, but how they relate to pathogenesis and whether these cells can serve as biomarkers of disease activity in humans deserve further exploration.

Roles of cytokines and T cells in the pathogenesis of myasthenia gravis

Myasthenia gravis (MG) is characterized by muscle weakness and fatigue caused by the presence of autoantibodies against the acetylcholine receptor (AChR) or the muscle-specific tyrosine kinase (MuSK). Activated T, B and plasma cells, as well as cytokines, play important roles in the production of pathogenic autoantibodies and the induction of inflammation at the neuromuscular junction in MG. Many studies have focused on the role of cytokines and lymphocytes in anti-AChR antibody-positive MG. Chronic inflammation mediated by T helper type 17 (Th17) cells, the promotion of autoantibody production from B cells and plasma cells by follicular Th (Tfh) cells and the activation of the immune response by dysfunction of regulatory T (T_reg ) cells may contribute to the exacerbation of the MG pathogenesis. In fact, an increased number of Th17 cells and Tfh cells and dysfunction of T_reg cells have been reported in patients with anti-AChR antibody-positive MG; moreover, the number of these cells was correlated with clinical parameters in patients with MG. Regarding cytokines, interleukin (IL)-17; a Th17-related cytokine, IL-21 (a Tfh-related cytokine), the B-cell-activating factor (BAFF; a B cell-related cytokine) and a proliferation-inducing ligand (APRIL; a B cell-related cytokine) have been reported to be up-regulated and associated with clinical parameters of MG. This review focuses on the current understanding of the involvement of cytokines and lymphocytes in the immunological pathogenesis of MG, which may lead to the development of novel therapies for this disease in the near future.

Thymus-derived B cell clones persist in the circulation after thymectomy in myasthenia gravis

Myasthenia gravis (MG) is a neuromuscular, autoimmune disease caused by autoantibodies that target postsynaptic proteins, primarily the acetylcholine receptor (AChR) and inhibit signaling at the neuromuscular junction. The majority of patients under 50 y with AChR autoantibody MG have thymic lymphofollicular hyperplasia. The MG thymus is a reservoir of plasma cells that secrete disease-causing AChR autoantibodies and although thymectomy improves clinical scores, many patients fail to achieve complete stable remission without additional immunosuppressive treatments. We speculate that thymus-associated B cells and plasma cells persist in the circulation after thymectomy and that their persistence could explain incomplete responses to resection. We studied patients enrolled in a randomized clinical trial and used complementary modalities of B cell repertoire sequencing to characterize the thymus B cell repertoire and identify B cell clones that resided in the thymus and circulation before and 12 mo after thymectomy. Thymus-associated B cell clones were detected in the circulation by both mRNA-based and genomic DNA-based sequencing. These antigen-experienced B cells persisted in the circulation after thymectomy. Many circulating thymus-associated B cell clones were inferred to have originated and initially matured in the thymus before emigration from the thymus to the circulation. The persistence of thymus-associated B cells correlated with less favorable changes in clinical symptom measures, steroid dose required to manage symptoms, and marginal changes in AChR autoantibody titer. This investigation indicates that the diminished clinical response to thymectomy is related to persistent circulating thymus-associated B cell clones.

Myeloid-derived suppressor cell and regulatory T cell frequencies in canine myasthenia gravis: A pilot study

Myasthenia gravis (MG) is a T cell-dependent, B cell-mediated autoimmune disease. Little is known about its cellular pathogenesis in dogs. This study provides the first preliminary assessment of the frequency of myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) in the peripheral blood of dogs with seropositive generalized MG. No alteration in frequency of either MDSCs or Tregs in dogs with MG was observed when compared to those in either seronegative dogs with diagnoses other than MG, or healthy dogs. A longitudinal study in three dogs with MG revealed no correlation between the relative numbers of either population and the clinical course of disease. Neither the frequency of MDSCs nor of Tregs showed a correlation with anti-AChR antibody titer in dogs with MG. These findings suggest that aberrations in the frequency of either immunosuppressive population do not occur in MG, but they need to be validated in large-scale prospective studies.

Autoimmune Pathology in Myasthenia Gravis Disease Subtypes Is Governed by Divergent Mechanisms of Immunopathology

Myasthenia gravis (MG) is a prototypical autoantibody mediated disease. The autoantibodies in MG target structures within the neuromuscular junction (NMJ), thus affecting neuromuscular transmission. The major disease subtypes of autoimmune MG are defined by their antigenic target. The most common target of pathogenic autoantibodies in MG is the nicotinic acetylcholine receptor (AChR), followed by muscle-specific kinase (MuSK) and lipoprotein receptor-related protein 4 (LRP4). MG patients present with similar symptoms independent of the underlying subtype of disease, while the immunopathology is remarkably distinct. Here we highlight these distinct immune mechanisms that describe both the B cell- and autoantibody-mediated pathogenesis by comparing AChR and MuSK MG subtypes. In our discussion of the AChR subtype, we focus on the role of long-lived plasma cells in the production of pathogenic autoantibodies, the IgG1 subclass mediated pathology, and contributions of complement. The similarities underlying the immunopathology of AChR MG and neuromyelitis optica (NMO) are highlighted. In contrast, MuSK MG is caused by autoantibody production by short-lived plasmablasts. MuSK MG autoantibodies are mainly of the IgG4 subclass which can undergo Fab-arm exchange (FAE), a process unique to this subclass. In FAE IgG4, molecules can dissociate into two halves and recombine with other half IgG4 molecules resulting in bispecific antibodies. Similarities between MuSK MG and other IgG4-mediated autoimmune diseases, including pemphigus vulgaris (PV) and chronic inflammatory demyelinating polyneuropathy (CIDP), are highlighted. Finally, the immunological distinctions are emphasized through presentation of biological therapeutics that provide clinical benefit depending on the MG disease subtype.

CD4+ T Cells of Myasthenia Gravis Patients Are Characterized by Increased IL-21, IL-4, and IL-17A Productions and Higher Presence of PD-1 and ICOS

Myasthenia gravis (MG) is an autoimmune disease mediated by autoantibodies predominantly against the acetylcholine receptor (AChR). Specific T cell subsets are required for long-term antibody responses, and cytokines secreted mainly from CD4⁺ T cells regulate B cell antibody production. The aim of this study was to assess the differences in the cytokine expressions of CD4⁺ T cells in MG patients with AChR antibodies (AChR-MG) and the effect of immunosuppressive (IS) therapy on cytokine activity and to test these findings also in MG patients without detectable antibodies (SN-MG). Clinically diagnosed AChR-MG and SN-MG patients were included. The AChR-MG patients were grouped as IS-positive and -negative and compared with age- and sex-matched healthy controls. Peripheral blood mononuclear cells were used for ex vivo intracellular cytokine production, and subsets of CD4⁺ T cells and circulating follicular helper T (cTfh) cells were detected phenotypically by the expression of the chemokine and the costimulatory receptors. Thymocytes obtained from patients who had thymectomy were also analyzed. IL-21, IL-4, IL-10, and IL-17A productions in CD4⁺ T cells were increased in AChR-MG compared to those in healthy controls. IS treatment enhanced IL-10 and reduced IFN-γ production in AChR-MG patients compared to those in IS-negative patients. Increased IL-21 and IL-4 productions were also demonstrated in SN-MG patients. Among CD4⁺ T cells, Th17 cells were increased in both disease subgroups. Treatment induced higher proportions of Th2 cells in AChR-MG patients. Both CXCR5⁺ and CXCR5⁻ CD4⁺ T cells expressed higher programmed cell death protein 1 (PD-1) and inducible costimulatory (ICOS) in AChR-MG and SN-MG groups, mostly irrespective of the treatment. Based on chemokine receptors on CXCR5⁺PD-1⁺ in CD4⁺ T (cTfh) cells, in AChR-MG patients without treatment, the proportions of Tfh17 cells were higher than those in the treated group, whereas the Tfh1 cells were decreased compared with those in the controls. The relevance of CXCR5 and PD-1 in the pathogenesis of AChR-MG was also suggested by the increased presence of these molecules on mature CD4 single-positive thymocytes from the thymic samples. The study provides further evidence for the importance of IL-21, IL-17A, IL-4, and IL-10 in AChR-MG. Disease-related CD4⁺T cells are identified mainly as PD-1⁺ or ICOS⁺ with or without CXCR5, resembling cTfh cells in the circulation or probably in the thymus. AChR-MG and SN-MG seem to have some similar characteristics. IS treatment has distinctive effects on cytokine expression.

Comparative Analysis of Thymic and Blood Treg in Myasthenia Gravis: Thymic Epithelial Cells Contribute to Thymic Immunoregulatory Defects

The thymus is involved in autoimmune Myasthenia gravis (MG) associated with anti-acetylcholine (AChR) antibodies. In MG, thymic regulatory T cells (Treg) are not efficiently suppressive, and conventional T cells (Tconv) are resistant to suppression. To better understand the specific role of the thymus in MG, we compared the phenotype and function of peripheral and thymic Treg and Tconv from controls and MG patients. Suppression assays with thymic or peripheral CD4 + T cells showed that the functional impairment in MG was more pronounced in the thymus than in the periphery. Phenotypic analysis of Treg showed a significant reduction of resting and effector Treg in the thymus but not in the periphery of MG patients. CD31, a marker lost with excessive immunoreactivity, was significantly reduced in thymic but not blood resting Treg. These results suggest that an altered thymic environment may explain Treg differences between MG patients and controls. Since thymic epithelial cells (TECs) play a major role in the generation of Treg, we co-cultured healthy thymic CD4 + T cells with control or MG TECs and tested their suppressive function. Co-culture with MG TECs consistently hampers regulatory activity, as compared with control TECs, suggesting that MG TECs contribute to the immune regulation defects of MG CD4 + T cells. MG TECs produced significantly higher thymic stromal lymphopoietin (TSLP) than control TECs, and a neutralizing anti-TSLP antibody partially restored the suppressive capacity of Treg derived from co-cultures with MG TECs, suggesting that TSLP contributed to the defect of thymic Treg in MG patients. Finally, a co-culture of MG CD4 + T cells with control TECs restored numbers and function of MG Treg, demonstrating that a favorable environment could correct the immune regulation defects of T cells in MG. Altogether, our data suggest that the severe defect of thymic Treg is at least partially due to MG TECs that overproduce TSLP. The Treg defects could be corrected by replacing dysfunctional TECs by healthy TECs. These findings highlight the role of the tissue environment on the immune regulation.

Advances in the role of helper T cells in autoimmune diseases

Autoimmune diseases are primary immune diseases in which autoreactive antibodies or sensitized lymphocytes destroy and damage tissue and cellular components, resulting in tissue damage and organ dysfunction. Helper T cells may be involved in the pathogenesis of autoimmune diseases under certain conditions. This review summarizes recent research on the role of helper T cells in autoimmune diseases from two aspects, helper T cell-mediated production of autoantibodies by B cells and helper T cell-induced activation of abnormal lymphocytes, and provides ideas for the treatment of autoimmune diseases. The abnormal expression of helper T cells promotes the differentiation of B cells that produce autoantibodies, which leads to the development of different diseases. Among them, abnormal expression of Th2 cells and T follicular helper cells is more likely to cause antibody-mediated autoimmune diseases. In addition, abnormal activation of helper T cells also mediates autoimmune diseases through the production of abnormal cytokines and chemokines. Helper T cells play an essential role in the pathogenesis of autoimmune diseases, and a full understanding of their role in autoimmune diseases is helpful for providing ideas for the treatment of autoimmune diseases.

The progress and prospect of regulatory T cells in autoimmune diseases

Regulatory T cells (Treg) are an important immune cell population, playing a crucial role in regulating immune tolerance and preventing autoimmune diseases. These cells consist of various cell sub-populations and generally have an immunoregulatory or suppressive role against immune responses. They also have a different cell heterogeneity and each populations has own biological characteristics. Treg deficiency, reduction, instability, reduced vitality and dysfunction all account for multiple autoimmune diseases. In this review, we have systemically reviewed Treg classification, phenotypic features, regulation of Foxp3 expression, plasticity and stability of Treg as well as their relationship with several important autoimmune diseases. We particularly focus on why and how inflammatory and diet environments affect the functional capacity and underlying mechanisms of Treg cell populations. We also summarize new advances in technologies which help to analyze and dissect these cells in molecular levels in-depth. We also clarify the possible clinical relevance on application of these cells in patients with autoimmune diseases. The advantages and weaknesses have been carefully discussed as well. We also propose the possible approaches to overcome these weaknesses of Treg cells in complicate environments. Thus, we have displayed the updated knowledge of Treg cells, which provides an overall insight into the role and mechanisms of Treg cells in autoimmune diseases.

Effects of Mitophagy on Regulatory T Cell Function in Patients With Myasthenia Gravis

Objective: This study was conducted to determine whether regulatory T cells (CD4⁺CD25⁺T, Tregs) show abnormal mitophagy as well as the function of Tregs in patients with myasthenia gravis (MG).

Methods: CD4⁺T cells and CD4⁺CD25⁺Treg cells were obtained from 15 patients with MG (MG group) and 15 controls (N group). Tregs from the MG group were subjected to rapamycin-induced culture for 48 h (Rapa group) and 3-methyladenine-induced culture for 48 h (3-MA group). The levels of mitophagy in Tregs were then observed through electron and confocal microscopy. Expression of the autophagy-related protein LC3-II was detected by western blotting, and mitochondrial function in each group was evaluated by flow cytometry. Inhibition of Treg cell proliferation was detected by flow cytometry.

Results: Mitophagy in the MG group was lower than that in the N group; it was higher in the Rapa group compared to that in the MG group and lowered in the 3-MA group than in the MG group. Expression of the autophagy-related protein LC3-II was lower in the MG group than in the N group, higher in the Rapa group than in the MG group, and lower in the 3-MA group than in the MG group. The mitochondrial membrane potential was lower in the MG group compared to that in the N group; it was higher in the Rapa group than in the MG group and lowered in the 3-MA group than in the MG group. Inhibition of Treg proliferation was lower in the MG group than in the N group; it was higher in the Rapa group than in the MG group and lowered in the 3-MA group than in the MG group.

Conclusion: The decreased mitochondrial membrane potential and mitophagy in Tregs in the MG group may be related to a decreased inhibition of Treg proliferation. The mitochondrial membrane potential was increased after adding the autophagy agent Rapa to enhance mitophagy, and the proliferation inhibition function of Tregs was also enhanced. The autophagy agent 3-MA down-regulated mitophagy, which decreased the mitochondrial membrane potential and inhibitory effect of Tregs. These results reveal the possible cellular immune mechanism of Treg dysfunction in MG.

miR-146a in Myasthenia Gravis Thymus Bridges Innate Immunity With Autoimmunity and Is Linked to Therapeutic Effects of Corticosteroids

Toll-like receptor (TLR)-mediated innate immune responses are critically involved in the pathogenesis of myasthenia gravis (MG), an autoimmune disorder affecting neuromuscular junction mainly mediated by antiacetylcholine receptor antibodies. Considerable evidence indicate that uncontrolled TLR activation and chronic inflammation significantly contribute to hyperplastic changes and germinal center (GC) formation in the MG thymus, ultimately leading to autoantibody production and autoimmunity. miR-146a is a key modulator of innate immunity, whose dysregulation has been associated with autoimmune diseases. It acts as inhibitor of TLR pathways, mainly by targeting the nuclear factor kappa B (NF-κB) signaling transducers, interleukin 1 receptor associated kinase 1 (IRAK1) and tumor necrosis factor (TNF) receptor associated factor 6 (TRAF6); miR-146a is also able to target c-REL, inducible T-cell costimulator (ICOS), and Fas cell surface death receptor (FAS), known to regulate B-cell function and GC response. Herein, we investigated the miR-146a contribution to the intrathymic MG pathogenesis. By real-time PCR, we found that miR-146a expression was significantly downregulated in hyperplastic MG compared to control thymuses; contrariwise, IRAK1, TRAF6, c-REL, and ICOS messenger RNA (mRNA) levels were upregulated and negatively correlated with miR-146a levels. Microdissection experiments revealed that miR-146a deficiency in hyperplastic MG thymuses was not due to GCs, but restricted to the GC-surrounding medulla, characterized by IRAK1 overexpression. We also showed higher c-REL and ICOS mRNA levels, and lower FAS mRNA levels, in GCs than in the remaining medulla, according to the contribution of these molecules in GC formation. By double immunofluorescence, an increased proportion of IRAK1-expressing dendritic cells and macrophages was found in hyperplastic MG compared to control thymuses, along with GC immunoreactivity for c-REL. Interestingly, in corticosteroid-treated MG patients intrathymic miR-146a and mRNA target levels were comparable to those of controls, suggesting that immunosuppressive therapy may restore the microRNA (miRNA) levels. Indeed, an effect of prednisone on miR-146a expression was demonstrated in vitro on peripheral blood cells. Serum miR-146a levels were lower in MG patients compared to controls, indicating dysregulation of the circulating miRNA. Our overall findings strongly suggest that defective miR-146a expression could contribute to persistent TLR activation, lack of inflammation resolution, and hyperplastic changes in MG thymuses, thus linking TLR-mediated innate immunity to B-cell-mediated autoimmunity. Furthermore, they unraveled a new mechanism of action of corticosteroids in inducing control of autoimmunity in MG via miR-146a.

Defects of CTLA-4 Are Associated with Regulatory T Cells in Myasthenia Gravis Implicated by Intravenous Immunoglobulin Therapy

Myasthenia gravis (MG) is a CD4⁺ T cell-dependent autoimmune disease resulting from aberrant immune response mediated by circulating autoantibodies at the neuromuscular junction. Intravenous immunoglobulin (IVIg) is an expensive and commonly used immunotherapeutic approach to treat patients with MG. The mechanisms of actions involved in IVIg treatment, however, remain to be investigated. In an effort to examine the roles of various subsets of CD4⁺ T cells in the periphery blood of MG and uncover the mechanisms that contribute to the therapeutical effects of IVIg, we first demonstrated that a subset of CD4⁺ T cells, CTLA-4-expressing regulatory T (Treg) cells, were underrepresented and functionally defective in MG patients. The dynamic profiling during the IVIg therapy course further revealed an inverse relationship between the frequency of CTLA-4⁺ Treg and the quantitative MG (QMG) score that represents disease severity. Our mechanistic studies indicated that IVIg expands CTLA-4-Treg cells via modulating antigen-presenting dendritic cells (DCs). To determine the molecular defects of CTLA-4 in abnormities of Treg in MG patients, we demonstrated hypermethylation at -658 and -793 CpGs of CTLA-4 promoter in MG Tregs. Interestingly, IVIg therapy significantly reduced the methylation level at these two sites in MG patients. Overall, our study may suggest a role of CTLA-4 in functionally defected Treg cells in MG and its actions involved in IVIg therapy.

Estrogen, estrogen-like molecules and autoimmune diseases

In western countries, the slope of autoimmune disease (AD) incidence is increasing and affects 5-8% of the population. Mainly prevalent in women, these pathologies are due to thymic tolerance processes breakdown. The female sex hormone, estrogen, is involved in this AD female susceptibility. However, predisposition factors have to act in concert with unknown triggering environmental factors (virus, microbiota, pollution) to initiate AD. Individuals are exposed to various environmental compounds that display endocrine disruption abilities. The cellular effects of some of these molecules may be mediated through the aryl hydrocarbon receptor (AhR). Here, we review the effects of these molecules on the homeostasis of the thymic cells, the immune tolerance intrinsic factors (transcription factors, epigenetic marks) and on the immune tolerance extrinsic factors (microbiota, virus sensibility). This review highlights the contribution of estrogen and endocrine disruptors on the dysregulation of mechanisms sustaining AD development.

Inhibition of the transcription factor ROR-γ reduces pathogenic Th17 cells in acetylcholine receptor antibody positive myasthenia gravis

IL-17 producing CD4 T cells (Th17) cells increase significantly with disease severity in myasthenia gravis (MG) patients. To suppress the generation of Th17 cells, we examined the effect of inhibiting retinoic acid receptor-related-orphan-receptor-C (RORγ), a Th17-specific transcription factor critical for differentiation. RORγ inhibition profoundly reduced Th17 cell frequencies, including IFN-γ and IL-17 co-producing pathogenic Th17 cells. Other T helper subsets were not affected. In parallel, CD8 T cell subsets producing IL-17 and IL-17/IFN-γ were increased in MG patients and inhibited by the RORγ inhibitor. These findings provide rationale for exploration of targeted Th17 therapies, including ROR-γ inhibitors, to treat MG patients.

Exosomes derived from statin-modified bone marrow dendritic cells increase thymus-derived natural regulatory T cells in experimental autoimmune myasthenia gravis

BACKGROUND

The thymus plays an essential role in the pathogenesis of myasthenia gravis (MG). In patients with MG, natural regulatory T cells (nTreg), a subpopulation of T cells that maintain tolerance to self-antigens, are severely impaired in the thymuses. In our previous study, upregulated nTreg cells were observed in the thymuses of rats in experimental autoimmune myasthenia gravis after treatment with exosomes derived from statin-modified dendritic cells (statin-Dex).

METHODS

We evaluated the effects of exosomes on surface co-stimulation markers and Aire expression of different kinds of thymic stromal cells, including cTEC, mTEC, and tDCs, in EAMG rats. The isolated exosomes were examined by western blot and DLS. Immunofluorescence was used to track the exosomes in the thymus. Flow cytometry and western blot were used to analyze the expression of co-stimulatory molecules and Aire in vivo and in vitro.

RESULTS

We confirmed the effects of statin-Dex in inducing Foxp3+ nTreg cells and found that both statin-Dex and DMSO-Dex could upregulate CD40 but only statin-Dex increased Aire expression in thymic stromal cells in vivo. Furthermore, we found that the role of statin-Dex and DMSO-Dex in the induction of Foxp3+ nTreg cells was dependent on epithelial cells in vitro.

CONCLUSIONS

We demonstrated that statin-Dex increased expression of Aire in the thymus, which may further promote the Foxp3 expression in the thymus. These findings may provide a new strategy for the treatment of myasthenia gravis.

Therapeutic potential of aryl hydrocarbon receptor in autoimmunity

Aryl hydrocarbon receptor (AhR), a type of transcriptional factor, is widely expressed in immune cells. The activation of AhR signaling pathway depends on its ligands, which exist in environment and can also be produced by metabolism. Normal expressions of AhR and AhR-mediated signaling may be essential for immune responses, and effects of AhR signaling on the development and function of innate and adaptive immune cells have also been revealed in previous studies. Recent studies also indicate that aberrant AhR signaling may be related to autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), autoimmune uveitis (AU), autoimmune diabetes, Behcet's disease (BD) and myasthenia gravis (MG). Moreover, administration of AhR ligands or drugs has been proven effective for improving pathological outcomes in some autoimmune diseases or models. In this review, we summarize the effects of AhR on several innate and adaptive immune cells associated with autoimmunity, and the mechanism on how AhR participates in autoimmune diseases. In addition, we also discuss therapeutic potential and application prospect of AhR in autoimmune diseases, so as to provide valuable information for exploring novel and effective approaches to autoimmune disease treatments.

Myasthenia gravis: State of the art and new therapeutic strategies

Myasthenia Gravis (MG) - an autoimmune neuromuscular disease - is known by the production of autoantibodies against components of the neuromuscular junction mainly to the acetylcholine receptor, which cause the destruction and compromises the synaptic transmission. This disease is characterized by fluctuating and fatigable muscle weakness, becoming more intensive with activity, but with an improvement under resting. There are many therapeutic strategies used to alleviate MG symptoms, either by improving the transmission of the nerve impulse or by ameliorating autoimmune reactions with e.g. steroids, immunosuppressant drugs, or monoclonal antibodies (rituximab and eculizumab). Many breakthroughs in the discovery of new therapeutic targets have been reported, but MG remains to be a chronic disease where the symptoms are kept in the majority of patients. In this review, we discuss the different therapeutic strategies that have been used over the years to alleviate MG symptoms, as well as innovative therapeutic approaches currently under study.

Myasthenia Gravis: Pathogenic Effects of Autoantibodies on Neuromuscular Architecture

Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction (NMJ). Autoantibodies target key molecules at the NMJ, such as the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low-density lipoprotein receptor-related protein 4 (Lrp4), that lead by a range of different pathogenic mechanisms to altered tissue architecture and reduced densities or functionality of AChRs, reduced neuromuscular transmission, and therefore a severe fatigable skeletal muscle weakness. In this review, we give an overview of the history and clinical aspects of MG, with a focus on the structure and function of myasthenic autoantigens at the NMJ and how they are affected by the autoantibodies' pathogenic mechanisms. Furthermore, we give a short overview of the cells that are implicated in the production of the autoantibodies and briefly discuss diagnostic challenges and treatment strategies.

Myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disease caused by antibodies against the acetylcholine receptor (AChR), muscle-specific kinase (MuSK) or other AChR-related proteins in the postsynaptic muscle membrane. Localized or general muscle weakness is the predominant symptom and is induced by the antibodies. Patients are grouped according to the presence of antibodies, symptoms, age at onset and thymus pathology. Diagnosis is straightforward in most patients with typical symptoms and a positive antibody test, although a detailed clinical and neurophysiological examination is important in antibody-negative patients. MG therapy should be ambitious and aim for clinical remission or only mild symptoms with near-normal function and quality of life. Treatment should be based on MG subgroup and includes symptomatic treatment using acetylcholinesterase inhibitors, thymectomy and immunotherapy. Intravenous immunoglobulin and plasma exchange are fast-acting treatments used for disease exacerbations, and intensive care is necessary during exacerbations with respiratory failure. Comorbidity is frequent, particularly in elderly patients. Active physical training should be encouraged.