Effects of cytokines on acetylcholine receptor expression: implications for myasthenia gravis

Dynamic changes of peripheral inflammatory markers link with disease severity and predict short-term poor outcome of myasthenia gravis

The relationship between peripheral inflammatory markers, their dynamic changes, and the disease severity of myasthenia gravis (MG) is still not fully understood. Besides, the possibility of using it to predict the short-term poor outcome of MG patients have not been demonstrated. This study aims to investigate the relationship between peripheral inflammatory markers and their dynamic changes with Myasthenia Gravis Foundation of America (MGFA) classification (primary outcome) and predict the short-term poor outcome (secondary outcome) in MG patients. The study retrospectively enrolled 154 MG patients from June 2016 to December 2021. The logistic regression was used to investigate the relationship of inflammatory markers with MGFA classification and determine the factors for model construction presented in a nomogram. Finally, net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were utilized to evaluate the incremental capacity. Logistic regression revealed significant associations between neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), aggregate index of systemic inflammation (AISI) and MGFA classification (p = 0.013, p = 0.032, p = 0.017, respectively). Incorporating dynamic changes of inflammatory markers into multivariable models improved their discriminatory capacity of disease severity, with significant improvements observed for NLR, systemic immune-inflammation index (SII) and AISI in NRI and IDI. Additionally, AISI was statistically associated with short-term poor outcome and a prediction model incorporating dynamic changes of inflammatory markers was constructed with the area under curve (AUC) of 0.953, presented in a nomograph. The inflammatory markers demonstrate significant associations with disease severity and AISI could be regarded as a possible and easily available predictive biomarker for short-term poor outcome in MG patients.

Interferon autoantibodies as signals of a sick thymus

Type I interferons (IFN-I) are key immune messenger molecules that play an important role in viral defense. They act as a bridge between microbe sensing, immune function magnitude, and adaptive immunity to fight infections, and they must therefore be tightly regulated. It has become increasingly evident that thymic irregularities and mutations in immune genes affecting thymic tolerance can lead to the production of IFN-I autoantibodies (autoAbs). Whether these biomarkers affect the immune system or tissue integrity of the host is still controversial, but new data show that IFN-I autoAbs may increase susceptibility to severe disease caused by certain viruses, including SARS-CoV-2, herpes zoster, and varicella pneumonia. In this article, we will elaborate on disorders that have been identified with IFN-I autoAbs, discuss models of how tolerance to IFN-Is is lost, and explain the consequences for the host.

Morphological and functional alterations of neuromuscular synapses in a mouse model of ACTA1 congenital myopathy

Mutations in skeletal muscle α-actin (Acta1) cause myopathies. In a mouse model of congenital myopathy, heterozygous Acta1 (H40Y) knock-in (Acta1+/Ki) mice exhibit features of human nemaline myopathy, including premature lethality, severe muscle weakness, reduced mobility, and the presence of nemaline rods in muscle fibers. In this study, we investigated the impact of Acta1 (H40Y) mutation on the neuromuscular junction (NMJ). We found that the NMJs were markedly fragmented in Acta1+/Ki mice. Electrophysiological analysis revealed a decrease in amplitude but increase in frequency of miniature end-plate potential (mEPP) at the NMJs in Acta1+/Ki mice, compared with those in wild type (Acta1+/+) mice. Evoked end-plate potential (EPP) remained similar at the NMJs in Acta1+/Ki and Acta1+/+ mice, but quantal content was increased at the NMJs in Acta1+/Ki, compared with Acta1+/+ mice, suggesting a homeostatic compensation at the NMJs in Acta1+/Ki mice to maintain normal levels of neurotransmitter release. Furthermore, short-term synaptic plasticity of the NMJs was compromised in Acta1+/Ki mice. Together, these results demonstrate that skeletal Acta1 H40Y mutation, albeit muscle-origin, leads to both morphological and functional defects at the NMJ.

Myasthenia gravis: Molecular mechanisms and promising therapeutic strategies

Myasthenia gravis (MG) is a type of autoimmune disease caused by the blockage of neuromuscular junction transmission owing to the attack of autoantibodies on transmission-related proteins. Related antibodies, such as anti-AChR, anti-MuSK and anti-LRP4 antibodies, can be detected in most patients with MG. Although traditional therapies can control most symptoms, several challenges remain to be addressed, necessitating the development of more effective and safe treatment strategies for MG. With the in-depth exploration on the mechanism and immune targets of MG, effective therapies, especially therapies using biologicals, have been reported recently. Given the important roles of immune cells, cytokines and intercellular interactions in the pathological process of MG, B-cell targeted therapy, T-cell targeted therapy, proteasome inhibitors targeting plasma cell, complement inhibitors, FcRn inhibitors have been developed for the treatment of MG. Although these novel therapies exert good therapeutic effects, they may weaken the immunity and increase the risk of infection in MG patients. This review elaborates on the pathogenesis of MG and discusses the advantages and disadvantages of the strategies of traditional treatment and biologicals. In addition, this review emphasises that combined therapy may have better therapeutic effects and reducing the risk of side effects of treatments, which has great prospects for the treatment of MG. With the deepening of research on immunotherapy targets in MG, novel opportunities and challenges in the treatment of MG will be introduced.

Inflammation and autoimmune myasthenia gravis

Myasthenia gravis (MG) is a neuromuscular autoimmune disorder characterized by chronic but intermittent fatigue of the eye- and general body muscles. Muscle weakness is caused primarily by the binding of an autoantibody to the acetylcholine receptors, resulting in blockage of normal neuromuscular signal transmission. Studies revealed substantial contributions of different proinflammatory or inflammatory mediators in the pathogenesis of MG. Despite these findings, compared to therapeutic approaches that target autoantibody and complements, only a few therapeutics against key inflammatory molecules have been designed or tested in MG clinical trials. Recent research focuses largely on identifying unknown molecular pathways and novel targets involved in inflammation associated with MG. A well-designed combination or adjunct treatment utilizing one or more selective and validated promising biomarkers of inflammation as a component of targeted therapy may yield better treatment outcomes. This review briefly discusses some preclinical and clinical findings of inflammation associated with MG and current therapy approaches and suggest the potential of targeting important inflammatory marker(s) along with current monoclonal antibody or antibody fragment based targeted therapies directed to a variety of cell surface receptors.

Myasthenia gravis-specific aberrant neuromuscular gene expression by medullary thymic epithelial cells in thymoma

Myasthenia gravis (MG) is a neurological disease caused by autoantibodies against neuromuscular-associated proteins. While MG frequently develops in thymoma patients, the etiologic factors for MG are not well understood. Here, by constructing a comprehensive atlas of thymoma using bulk and single-cell RNA-sequencing, we identify ectopic expression of neuromuscular molecules in MG-type thymoma. These molecules are found within a distinct subpopulation of medullary thymic epithelial cells (mTECs), which we name neuromuscular mTECs (nmTECs). MG-thymoma also exhibits microenvironments dedicated to autoantibody production, including ectopic germinal center formation, T follicular helper cell accumulation, and type 2 conventional dendritic cell migration. Cell–cell interaction analysis also predicts the interaction between nmTECs and T/B cells via CXCL12-CXCR4. The enrichment of nmTECs presenting neuromuscular molecules within MG-thymoma is further confirmed immunohistochemically and by cellular composition estimation from the MG-thymoma transcriptome. Altogether, this study suggests that nmTECs have a significant function in MG pathogenesis via ectopic expression of neuromuscular molecules.

Poor responses and adverse outcomes of myasthenia gravis after thymectomy: Predicting factors and immunological implications

Myasthenia gravis (MG) has been recognized as a series of heterogeneous but treatable autoimmune conditions. As one of the indispensable therapies, thymectomy can achieve favorable prognosis especially in early-onset generalized MG patients with seropositive acetylcholine receptor antibody. However, poor outcomes, including worsening or relapse of MG, postoperative myasthenic crisis and even post-thymectomy MG, are also observed in certain scenarios. The responses to thymectomy may be associated with the general characteristics of patients, disease conditions of MG, autoantibody profiles, native or ectopic thymic pathologies, surgical-related factors, pharmacotherapy and other adjuvant modalities, and the presence of comorbidities and complications. However, in addition to these variations among individuals, pathological remnants and the abnormal immunological milieu and responses potentially represent major mechanisms that underlie the detrimental neurological outcomes after thymectomy. We underscore these plausible risk factors and discuss the immunological implications therein, which may be conducive to better managing the indications for thymectomy, to avoiding modifiable risk factors of poor responses and adverse outcomes, and to developing post-thymectomy preventive and therapeutic strategies for MG.

LncRNA LINC00680 Acts as a Competing Endogenous RNA and Is Associated With the Severity of Myasthennia Gravis

Background and Purpose

Myasthenia gravis (MG) is a T cell-dependent antibody-mediated autoimmune disorder that can seriously affect patients' quality of life. However, few studies have focused on the severity of MG. Moreover, existing therapeutic efforts, including those targeting biomarkers for MG, remain unsatisfactory. Therefore, it is vital that we investigate the pathogenesis of MG and identify new biomarkers that can not only evaluate the severity of the disease but also serve as potential therapeutic targets. Long noncoding RNA LINC00680 has been found to be associated with the progression of a variety of diseases as a competing endogenous RNA (ceRNA). However, the specific role of LINC00680 in MG has yet to be clarified. Here, we aimed to investigate the association between LINC00680 and the severity of MG.

Methods

Bioinformatics tools, quantitative real-time PCR, Western blotting, and luciferase assays were selected to investigate key signaling pathways and RNA expression in patients with MG. The Quantitative MG Score scale and the MG Composite scale were used to evaluate the severity of MG in the included patients. Cell viability assays and flow cytometry analysis were selected to analyze cell proliferation and apoptosis.

Results

Compared with control subjects, the expression levels of LINC00680 and mitogen-activated protein kinase 1 (MAPK1) in peripheral blood mononuclear cells of patients with MG were both upregulated; the levels of miR-320a were downregulated. A positive correlation was detected between LINC00680 expression and the severity of MG. Luciferase reporter assays identified that LINC00680 acts as a target for miR-320a. The in vitro analysis confirmed that LINC00680 regulates the expression of MAPK1 by sponging miR-320a. Finally, the functional analysis indicated that LINC00680 promoted Jurkat cell proliferation and inhibited cellular apoptosis by sponging miR-320a.

Conclusion

LINC00680 may be associated with the severity of MG as a ceRNA by sponging miR-320a to upregulate MAPK1. These findings suggest that LINC00680 may represent a potential biomarker which evaluates the severity of MG and may serve as a therapeutic target.

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.

A Targeted Complement Inhibitor CRIg/FH Protects Against Experimental Autoimmune Myasthenia Gravis in Rats via Immune Modulation

Antibody-induced complement activation may cause injury of the neuromuscular junction (NMJ) and is thus considered as a primary pathogenic factor in human myasthenia gravis (MG) and animal models of experimental autoimmune myasthenia gravis (EAMG). In this study, we tested whether CRIg/FH, a targeted complement inhibitor, could attenuate NMJ injury in rat MG models. We first demonstrated that CRIg/FH could inhibit complement-dependent cytotoxicity on human rhabdomyosarcoma TE671 cells induced by MG patient-derived IgG in vitro. Furthermore, we investigated the therapeutic effect of CRIg/FH in a passive and an active EAMG rodent model. In both models, administration of CRIg/FH could significantly reduce the complement-mediated end-plate damage and suppress the development of EAMG. In the active EAMG model, we also found that CRIg/FH treatment remarkably reduced the serum concentration of autoantibodies and of the cytokines including IFN-γ, IL-2, IL-6, and IL-17, and upregulated the percentage of Treg cells in the spleen, which was further verified in vitro. Therefore, our findings indicate that CRIg/FH may hold the potential for the treatment of MG via immune modulation.

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.

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.

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.

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.

Il-23/Th17 cell pathway: A promising target to alleviate thymic inflammation maintenance in myasthenia gravis

IL-23/Th17 pathway has been identified to sustain inflammatory condition in several autoimmune diseases and therefore being targeted in various therapeutic and effective approaches. Patients affected with autoimmune myasthenia gravis exhibit a disease effector tissue, the thymus, that harbors ectopic germinal centers that sustain production of auto-antibodies, targeting proteins located in the neuromuscular junction, cause of the organ-specific chronic autoimmune disease. The present study aims to investigate the IL-23/Th17 cell pathway in the thymic inflammatory and pathogenic events. We found that thymuses of MG patients displayed overexpression of Interleukin-17, signature cytokine of activated Th17 cells. This activation was sustained by a higher secretion of Interleukin-23 by TEC, in addition to the increased expression of cytokines involved in Th17 cell development. The overexpression of Interleukin-23 was due to a dysregulation of interferon type I pathway. Besides, Interleukin-17 secreted, and Th17 cells were localized around thymic ectopic germinal centers. These cells expressed podoplanin, a protein involved in B-cell maturation and antibody secretion. Finally, production of Interleukin-23 was also promoted by Interleukin-17 secreted itself by Th17 cells, highlighting a chronic loop of inflammation sustained by thymic cell interaction. Activation of the IL-23/Th17 pathway in the thymus of autoimmune myasthenia gravis patients creates an unstoppable loop of inflammation that may participate in ectopic germinal center maintenance. To alleviate the physio-pathological events in myasthenia gravis patients, this pathway may be considered as a new therapeutic target.

Advances in autoimmune myasthenia gravis management

INTRODUCTION

Myasthenia gravis (MG) is an autoimmune neuromuscular disorder with no cure and conventional treatments limited by significant adverse effects and variable benefit. In the last decade, therapeutic development has expanded based on improved understanding of autoimmunity and financial incentives for drug development in rare disease. Clinical subtypes exist based on age, gender, thymic pathology, autoantibody profile, and other poorly defined factors, such as genetics, complicate development of specific therapies. Areas covered: Clinical presentation and pathology vary considerably among patients with some having weakness limited to the ocular muscles and others having profound generalized weakness leading to respiratory insufficiency. MG is an antibody-mediated disorder dependent on autoreactive B cells which require T-cell support. Treatments focus on elimination of circulating autoantibodies or inhibition of effector mechanisms by a broad spectrum of approaches from plasmapheresis to B-cell elimination to complement inhibition. Expert commentary: Standard therapies and those under development are disease modifying and not curative. As a rare disease, clinical trials are challenged in patient recruitment. The great interest in development of treatments specific for MG is welcome, but decisions will need to be made to focus on those that offer significant benefits to patients.

Evidence for association of STAT4 and IL12RB2 variants with Myasthenia gravis susceptibility: What is the effect on gene expression in thymus?

Myasthenia gravis (MG) is an autoimmune disease mediated by the presence of autoantibodies that bind mainly to the acetylcholine receptor (AChR) in the neuromuscular junction. In our case-control association study, we analyzed common variants located in genes of the IL12/STAT4 and IL10/STAT3 signaling pathways. A total of 175 sporadic MG patients of Greek descent, positively detected with anti-AChR autoantibodies and 84 ethnically-matched, healthy volunteers were enrolled in the study. Thymus samples were obtained from 16 non-MG individuals for relative gene expression analysis. The strongest signals of association were observed in the cases of rs6679356 between the late-onset MG patients and controls and rs7574865 between early-onset MG and controls. Our investigation of the correlation between the MG-associated variants and the expression levels of each gene in thymus did not result in significant differences.

Toll-like receptors 7 and 9 in myasthenia gravis thymus: amplifiers of autoimmunity?

Pathogen infections and dysregulated Toll-like receptor (TLR)-mediated innate immune responses are suspected to play key roles in autoimmunity. Among TLRs, TLR7 and TLR9 have been implicated in several autoimmune conditions, mainly because of their ability to promote abnormal B cell activation and survival. Recently, we provided evidence of Epstein-Barr virus (EBV) persistence and reactivation in the thymus of myasthenia gravis (MG) patients, suggesting an involvement of EBV in the intrathymic pathogenesis of the disease. Considerable data highlight the existence of pathogenic crosstalk among EBV, TLR7, and TLR9: EBV elicits TLR7/9 signaling, which in turn can enhance B cell dysfunction and autoimmunity. In this article, after a brief summary of data demonstrating TLR activation in MG thymus, we provide an overview on the contribution of TLR7 and TLR9 to autoimmune diseases and discuss our recent findings indicating a pivotal role for these two receptors, along with EBV, in driving, perpetuating, and/or amplifying intrathymic B cell dysregulation and autoimmune responses in MG. Development of therapeutic approaches targeting TLR7 and TLR9 signaling could be a novel strategy for treating the chronic inflammatory autoimmune process in myasthenia gravis.

Muscle satellite cells are functionally impaired in myasthenia gravis: consequences on muscle regeneration

Myasthenia gravis (MG) is a neuromuscular disease caused in most cases by anti-acetyl-choline receptor (AChR) autoantibodies that impair neuromuscular signal transmission and affect skeletal muscle homeostasis. Myogenesis is carried out by muscle stem cells called satellite cells (SCs). However, myogenesis in MG had never been explored. The aim of this study was to characterise the functional properties of myasthenic SCs as well as their abilities in muscle regeneration. SCs were isolated from muscle biopsies of MG patients and age-matched controls. We first showed that the number of Pax7+ SCs was increased in muscle sections from MG and its experimental autoimmune myasthenia gravis (EAMG) mouse model. Myoblasts isolated from MG muscles proliferate and differentiate more actively than myoblasts from control muscles. MyoD and MyoG were expressed at a higher level in MG myoblasts as well as in MG muscle biopsies compared to controls. We found that treatment of control myoblasts with MG sera or monoclonal anti-AChR antibodies increased the differentiation and MyoG mRNA expression compared to control sera. To investigate the functional ability of SCs from MG muscle to regenerate, we induced muscle regeneration using acute cardiotoxin injury in the EAMG mouse model. We observed a delay in maturation evidenced by a decrease in fibre size and MyoG mRNA expression as well as an increase in fibre number and embryonic myosin heavy-chain mRNA expression. These findings demonstrate for the first time the altered function of SCs from MG compared to control muscles. These alterations could be due to the anti-AChR antibodies via the modulation of myogenic markers resulting in muscle regeneration impairment. In conclusion, the autoimmune attack in MG appears to have unsuspected pathogenic effects on SCs and muscle regeneration, with potential consequences on myogenic signalling pathways, and subsequently on clinical outcome, especially in the case of muscle stress.

Balance between Estrogens and Proinflammatory Cytokines Regulates Chemokine Production Involved in Thymic Germinal Center Formation

The early-onset form of Myasthenia Gravis (MG) is prevalent in women and associates with ectopic germinal centers (GCs) development and inflammation in the thymus. we aimed to investigate the contribution of estrogens in the molecular processes involved in thymic GCs formation. We examined expression of genes involved in anti-acetylcholine receptor (AChR) response in MG, MHC class II and α-AChR subunit as well as chemokines involved in GC development (CXCL13, CCL21and CXCL12). In resting conditions, estrogens have strong regulatory effects on thymic epithelial cells (TECs), inducing a decreased protein expression of the above molecules. In knockout mouse models for estrogen receptor or aromatase, we observed that perturbation in estrogen transduction pathway altered MHC Class II, α-AChR, and CXCL13 expression. However, in inflammatory conditions, estrogen effects were partially overwhelmed by pro-inflammatory cytokines. Interestingly, estrogens were able to control production of type I interferon and therefore play dual roles during inflammatory events. In conclusion, we showed that estrogens inhibited expression of α-AChR and HLA-DR in TECs, suggesting that estrogens may alter the tolerization process and favor environment for an autoimmune response. By contrast, under inflammatory conditions, estrogen effects depend upon strength of the partner molecules with which it is confronted to.

Review on Toll-Like Receptor Activation in Myasthenia Gravis: Application to the Development of New Experimental Models

Abnormal toll-like receptor (TLR) activation and uncontrolled resolution of inflammation are suspected to play a key role in the development of autoimmune diseases. Acquired myasthenia gravis (MG) is an invalidating neuromuscular disease leading to muscle weaknesses. MG is mainly mediated by anti-acetylcholine receptor (AChR) autoantibodies, and thymic hyperplasia characterized by ectopic germinal centers is a common feature in MG. An abnormal expression of certain TLRs is observed in the thymus of MG patients associated with the overexpression of interferon (IFN)-β, the orchestrator of thymic changes in MG. Experimental models have been developed for numerous autoimmune diseases. These models are induced by animal immunization with a purified antigen solubilized in complete Freund's adjuvant (CFA) containing heat-inactivated mycobacterium tuberculosis (MTB). Sensitization against the antigen is mainly due to the activation of TLR signaling pathways by the pathogen motifs displayed by MTB, and attempts have been made to substitute the use of CFA by TLR agonists. AChR emulsified in CFA is used to induce the classical experimental autoimmune MG model (EAMG). However, the TLR4 activator lipopolysaccharide (LPS) has proved to be efficient to replace MTB and induce a sensitization against purified AChR. Poly(I:C), the well-known TLR3 agonist, is also able by itself to induce MG symptoms in mice associated with early thymic changes as observed in human MG. In this review, we discuss the abnormal expression of TLRs in MG patients and we describe the use of TLR agonists to induce EAMG in comparison with other autoimmune experimental models.

Thymic Germinal Centers and Corticosteroids in Myasthenia Gravis: an Immunopathological Study in 1035 Cases and a Critical Review

The most common form of Myasthenia gravis (MG) is due to anti-acetylcholine receptor (AChR) antibodies and is frequently associated with thymic pathology. In this review, we discuss the immunopathological characteristics and molecular mechanisms of thymic follicular hyperplasia, the effects of corticosteroids on this thymic pathology, and the role of thymic epithelial cells (TEC), a key player in the inflammatory thymic mechanisms. This review is based not only on the literature data but also on thymic transcriptome results and analyses of pathological and immunological correlations in a vast cohort of 1035 MG patients without thymoma. We show that among patients presenting a thymic hyperplasia with germinal centers (GC), 80 % are females, indicating that thymic follicular hyperplasia is mainly a disease of women. The presence of anti-AChR antibodies is correlated with the degree of follicular hyperplasia, suggesting that the thymus is a source of anti-AChR antibodies. The degree of hyperplasia is not dependent upon the time from the onset, implying that either the antigen is chronically expressed and/or that the mechanisms of the resolution of the GC are not efficiently controlled. Glucocorticoids, a conventional therapy in MG, induce a significant reduction in the GC number, together with changes in the expression of chemokines and angiogenesis. These changes are likely related to the acetylation molecular process, overrepresented in corticosteroid-treated patients, and essential for gene regulation. Altogether, based on the pathological and molecular thymic abnormalities found in MG patients, this review provides some explanations for the benefit of thymectomy in early-onset MG patients.

Clinical features, pathogenesis, and treatment of myasthenia gravis: a supplement to the Guidelines of the German Neurological Society

Myasthenia gravis (MG) is an autoimmune antibody-mediated disorder of neuromuscular synaptic transmission. The clinical hallmark of MG consists of fluctuating fatigability and weakness affecting ocular, bulbar and (proximal) limb skeletal muscle groups. MG may either occur as an autoimmune disease with distinct immunogenetic characteristics or as a paraneoplastic syndrome associated with tumors of the thymus. Impairment of central thymic and peripheral self-tolerance mechanisms in both cases is thought to favor an autoimmune CD4(+) T cell-mediated B cell activation and synthesis of pathogenic high-affinity autoantibodies of either the IgG1 and 3 or IgG4 subclass. These autoantibodies bind to the nicotinic acetylcholine receptor (AchR) itself, or muscle-specific tyrosine-kinase (MuSK), lipoprotein receptor-related protein 4 (LRP4) and agrin involved in clustering of AchRs within the postsynaptic membrane and structural maintenance of the neuromuscular synapse. This results in disturbance of neuromuscular transmission and thus clinical manifestation of the disease. Emphasizing evidence from clinical trials, we provide an updated overview on immunopathogenesis, and derived current and future treatment strategies for MG divided into: (a) symptomatic treatments facilitating neuromuscular transmission, (b) antibody-depleting treatments, and

IL-6 and Akt are involved in muscular pathogenesis in myasthenia gravis

Introduction

Anti-acetylcholine receptor (AChR) autoantibodies target muscles in spontaneous human myasthenia gravis (MG) and its induced experimental autoimmune model MG (EAMG). The aim of this study was to identify novel functional mechanisms occurring in the muscle pathology of myasthenia.

Results

A transcriptome analysis performed on muscle tissue from MG patients (compared with healthy controls) and from EAMG rats (compared with control rats) revealed a deregulation of genes associated with the Interleukin-6 (IL-6) and Insulin-Like Growth Factor 1 (IGF-1) pathways in both humans and rats. The expression of IL-6 and its receptor IL-6R transcripts was found to be altered in muscles of EAMG rats and mice compared with control animals. In muscle biopsies from MG patients, IL-6 protein level was higher than in control muscles. Using cultures of human muscle cells, we evaluated the effects of anti-AChR antibodies on IL-6 production and on the phosphorylation of Protein Kinase B (PKB/Akt). Most MG sera and some monoclonal anti-AChR antibodies induced a significant increase in IL-6 production by human muscle cells. Furthermore, Akt phosphorylation in response to insulin was decreased in the presence of monoclonal anti-AChR antibodies.

Conclusions

Anti-AChR antibodies alter IL-6 production by muscle cells, suggesting a putative novel functional mechanism of action for the anti-AChR antibodies. IL-6 is a myokine with known effects on signaling pathways such as Akt/mTOR (mammalian Target of Rapamycin). Since Akt plays a key role in multiple cellular processes, the reduced phosphorylation of Akt by the anti-AChR antibodies may have a significant impact on the muscle fatigability observed in MG patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-014-0179-6) contains supplementary material, which is available to authorized users.

Biomechanical strain vehicles for fibroblast-directed skeletal myoblast differentiation and myotube functionality in a novel coculture

Skeletal muscle functionality is governed by multiple stimuli, including cytokines and biomechanical strain. Fibroblasts embedded within muscle connective tissue respond to biomechanical strain by secreting cytokines that induce myoblast differentiation and, we hypothesize, regulate myotube function. A coculture was established to allow cross talk between fibroblasts in Bioflex wells and myoblasts on nondeformable coverslips situated above Bioflex wells. Cyclic short-duration strain (CSDS) modeling repetitive stress/injury, acyclic long-duration strain (ALDS) modeling manipulative therapy, and combined strain paradigms (CSDS + ALDS) were applied to fibroblasts. Nonstrained myoblasts in uniculture and coculture served as controls. After fibroblasts had induced myoblast differentiation, myotube contraction was assessed by perfusion of ACh (10(-11)-10(-3) M). CSDS-treated fibroblasts increased myotube contractile sensitivity vs. uniculture (P < 0.05). As contraction is dependent on ACh binding, expression and clustering of nicotinic ACh receptors (nAChRs) were measured. CSDS-treated fibroblasts increased nAChR expression (P < 0.05), which correlated with myotube contraction. ALDS-treated fibroblasts did not significantly affect contraction or nAChR expression. Agrin-treated myotubes were then used to design a computer algorithm to identify α-bungarotoxin-stained nAChR clusters. ALDS-treated fibroblasts increased nAChR clustering (P < 0.05), while CSDS-treated fibroblasts disrupted cluster formation. CSDS-treated fibroblasts produced nAChRs preferentially located in nonclustered regions (P < 0.05). Strain-activated fibroblasts mediate myotube differentiation with multiple functional phenotypes. Similar to muscle injury, CSDS-treated fibroblasts disrupted nAChR clusters and hypersensitized myotube contraction, while ALDS-treated fibroblasts aggregated nAChRs in large clusters, which may have important clinical implications. Cellular strategies aimed at improving muscle functionality, such as through biomechanical strain vehicles that activate fibroblasts to stabilize postsynaptic nAChRs on nearby skeletal muscle, may serve as novel targets in neuromuscular disorders.

Cholinergic epithelial cell with chemosensory traits in murine thymic medulla

Specialized epithelial cells with a tuft of apical microvilli (“brush cells”) sense luminal content and initiate protective reflexes in response to potentially harmful substances. They utilize the canonical taste transduction cascade to detect “bitter” substances such as bacterial quorum-sensing molecules. In the respiratory tract, most of these cells are cholinergic and are approached by cholinoceptive sensory nerve fibers. Utilizing two different reporter mouse strains for the expression of choline acetyltransferase (ChAT), we observed intense labeling of a subset of thymic medullary cells. ChAT expression was confirmed by in situ hybridization. These cells showed expression of villin, a brush cell marker protein, and ultrastructurally exhibited lateral microvilli. They did not express neuroendocrine (chromogranin A, PGP9.5) or thymocyte (CD3) markers but rather thymic epithelial (CK8, CK18) markers and were immunoreactive for components of the taste transduction cascade such as Gα-gustducin, transient receptor potential melastatin-like subtype 5 channel (TRPM5), and phospholipase C_β2. Reverse transcription and polymerase chain reaction confirmed the expression of Gα-gustducin, TRPM5, and phospholipase C_β2. Thymic “cholinergic chemosensory cells” were often in direct contact with medullary epithelial cells expressing the nicotinic acetylcholine receptor subunit α3. These cells have recently been identified as terminally differentiated epithelial cells (Hassall’s corpuscle-like structures in mice). Contacts with nerve fibers (identified by PGP9.5 and CGRP antibodies), however, were not observed. Our data identify, in the thymus, a previously unrecognized presumptive chemosensitive cell that probably utilizes acetylcholine for paracrine signaling. This cell might participate in intrathymic infection-sensing mechanisms.

Fusion protein of single-chain variable domain fragments for treatment of myasthenia gravis

Single-chain variable domain fragment (scFv) 637 is an antigen-specific scFv of myasthenia gravis. In this study, scFv and human serum albumin genes were conjugated and the fusion protein was expressed in Pichia pastoris. The affinity of scFv-human serum albumin fusion protein to bind to acetylcholine receptor at the neuromuscular junction of human intercostal muscles was detected by immunofluorescence staining. The ability of the fusion protein to block myasthenia gravis patient sera binding to acetylcholine receptors and its stability in healthy serum were measured by competitive ELISA. The results showed that the inhibition rate was 2.0-77.4%, and the stability of fusion protein in static healthy sera was about 3 days. This approach suggests the scFv-human serum albumin is a potential candidate for specific immunosuppressive therapy of myasthenia gravis.

Terminally differentiated epithelial cells of the thymic medulla and skin express nicotinic acetylcholine receptor subunit α 3

In the thymus, T cell maturation is influenced by cholinergic signaling, and the predominantly expressed receptor is the α3-subunit of nicotinic acetylcholine receptors, encoded by the chrna3 gene. We here determined its cellular distribution utilizing an appropriate eGFP-expressing reporter mouse strain. Neither T cells (CD4, CD8) nor mesenchymal cells (desmin-positive) expressed eGFP. In the thymic medulla, eGFP-positive cells either were scattered or, more frequently, formed small clusters resembling Hassall's corpuscles. Immunolabeling revealed that these cells were indeed terminally differentiated epithelial cells expressing keratin 10 (K10) but neither typical cortical (K8, K18) nor medullary keratins (K5, K14). These labeling patterns reflected those in the epidermis of the skin, where overlap of K10 and eGFP expression was seen in the stratum granulosum, whereas underlying basal cells displayed K5-immunoreactivity. A substantial portion of thymic eGFP-positive cells was also immunoreactive to chromogranin A, a peptide previously reported in epidermal keratinocytes in the stratum granulosum. Its fragment catestatin has multiple biological activities, including suppression of proinflammatory cytokine release from macrophages and inhibition of α3β4 nAChR. The present findings suggest that its thymic production and/or release are under cholinergic control involving nAChR containing the α3-subunit.

Myasthenia Gravis: paradox versus paradigm in autoimmunity

Myasthenia Gravis (MG) is a paradigm of organ-specific autoimmune disease (AID). It is mediated by antibodies that target the neuromuscular junction. The purpose of this review is to place MG in the general context of autoimmunity, to summarize the common mechanisms between MG and other AIDs, and to describe the specific mechanisms of MG. We have chosen the most common organ-specific AIDs to compare with MG: type 1 diabetes mellitus (T1DM), autoimmune thyroid diseases (AITD), multiple sclerosis (MS), some systemic AIDs (systemic lupus erythematous (SLE), rheumatoid arthritis (RA), Sjogren's syndrome (SS)), as well as inflammatory diseases of the gut and liver (celiac disease (CeD), Crohn's disease (CD), and primary biliary cirrhosis (PBC)). Several features are similar between all AIDs, suggesting that common pathogenic mechanisms lead to their development. In this review, we address the predisposing factors (genetic, epigenetic, hormones, vitamin D, microbiota), the triggering components (infections, drugs) and their interactions with the immune system [1,2]. The dysregulation of the immune system is detailed and includes the role of B cells, Treg cells, Th17 and cytokines. We particularly focused on the role of TNF-α and interferon type I whose role in MG is very analogous to that in several other AIDS. The implication of AIRE, a key factor in central tolerance is also discussed. Finally, if MG is a prototype of AIDS, it has a clear specificity compared to the other AIDS, by the fact that the target organ, the muscle, is not the site of immune infiltration and B cell expansion, but exclusively that of antibody-mediated pathogenic mechanisms. By contrast, the thymus in the early onset subtype frequently undergoes tissue remodeling, resulting in the development of ectopic germinal centers surrounded by high endothelial venules (HEV), as observed in the target organs of many other AIDs.

Central role of interferon-beta in thymic events leading to myasthenia gravis

The thymus plays a primary role in early-onset Myasthenia Gravis (MG) mediated by anti-acetylcholine receptor (AChR) antibodies. As we recently showed an inflammatory and anti-viral signature in MG thymuses, we investigated in detail the contribution of interferon (IFN)-I and IFN-III subtypes in thymic changes associated with MG. We showed that IFN-I and IFN-III subtypes, but especially IFN-β, induced specifically α-AChR expression in thymic epithelial cells (TECs). We also demonstrated that IFN-β increased TEC death and the uptake of TEC proteins by dendritic cells. In parallel, we showed that IFN-β increased the expression of the chemokines CXCL13 and CCL21 by TECs and lymphatic endothelial cells, respectively. These two chemokines are involved in germinal center (GC) development and overexpressed in MG thymus with follicular hyperplasia. We also demonstrated that the B-cell activating factor (BAFF), which favors autoreactive B-cells, was overexpressed by TECs in MG thymus and was also induced by IFN-β in TEC cultures. Some of IFN-β effects were down-regulated when cell cultures were treated with glucocorticoids, a treatment widely used in MG patients that decreases the number of thymic GCs. Similar changes were observed in vivo. The injections of Poly(I:C) to C57BL/6 mice triggered a thymic overexpression of IFN-β and IFN-α2 associated with increased expressions of CXCL13, CCL21, BAFF, and favored the recruitment of B cells. These changes were not observed in the thymus of IFN-I receptor KO mice injected with Poly(I:C), even if IFN-β and IFN-α2 were overexpressed. Altogether, these results demonstrate that IFN-β could play a central role in thymic events leading to MG by triggering the overexpression of α-AChR probably leading to thymic DC autosensitization, the abnormal recruitment of peripheral cells and GC formation.

Myasthenia gravis: a comprehensive review of immune dysregulation and etiological mechanisms

Autoimmune myasthenia gravis (MG) is characterized by muscle weakness caused by antibodies directed against proteins of the neuromuscular junction. The main antigenic target is the acetylcholine receptor (AChR), but the muscle Specific Kinase (MuSK) and the low-density lipoprotein receptor-related protein (LRP4) are also targets. This review summarizes the clinical and biological data available for different subgroups of patients, who are classified according to antigenic target, age of onset, and observed thymic abnormalities, such as follicular hyperplasia or thymoma. Here, we analyze in detail the role of the thymus in the physiopathology of MG and propose an explanation for the development of the thymic follicular hyperplasia that is commonly observed in young female patients with anti-AChR antibodies. The influence of the pro-inflammatory environment is discussed, particularly the role of TNF-α and Th17-related cytokines, which could explain the escape of thymic T cells from regulation and the chronic inflammation in the MG thymus. Together with this immune dysregulation, active angiogenic processes and the upregulation of chemokines could promote thymic follicular hyperplasia. MG is a multifactorial disease, and we review the etiological mechanisms that could lead to its onset. Recent global genetic analyses have highlighted potential susceptibility genes. In addition, miRNAs, which play a crucial role in immune function, have been implicated in MG by recent studies. We also discuss the role of sex hormones and the influence of environmental factors, such as the viral hypothesis. This hypothesis is supported by reports that type I interferon and molecules mimicking viral infection can induce thymic changes similar to those observed in MG patients with anti-AChR antibodies.

[Myasthenia gravis and autoantibodies: Pathophysiology of the different subtypes]

Myasthenia gravis is characterized by muscle weakness and abnormal fatigability. It is an autoimmune disease caused by the presence of antibodies against components of the muscle membrane localized at the neuromuscular junction. In most cases, the autoantibodies are directed against the acetylcholine receptor (AChR). Recently, other targets have been described, such as muscle-specific kinase protein (MuSK) or lipoprotein related protein 4 (LRP4). The origin of the autoimmune response is not known, but thymic abnormalities and defects in immune regulation certainly play a major role in patients with anti-AChR antibodies. Genetic predisposition probably influences the occurrence of the disease. Sex hormones seem to play a role in the early form of the disease. Muscle weakness is fluctuating and worsens with exercise. Myasthenia gravis could be classified according to the location of the affected muscles (ocular versus generalized), the age of onset of symptoms, thymic abnormalities and profile of autoantibodies. These criteria are used to optimize the management and treatment of patients. In this review, we analyze the latest concepts of the pathophysiology of myasthenia gravis according to the different subgroups of the disease, including a description of the role of immunological, genetic and environmental factors. The potential viral hypothesis of this disease is discussed. Finally, we also discuss the biological assays available to validate the diagnosis.

Modeling the intrathymic pathogenesis of myasthenia gravis

Myasthenia gravis is (MG) a prototypic autoimmune disease; the immune effector mechanisms and autoantigenic target have been delineated. However, the events that lead to the abrogation of self-tolerance to neuromuscular acetylcholine receptors (nAChRs) remain a mystery. The thymus gland has long been considered to hold the key to solving this mystery, although the nature of its involvement remains to be elucidated. The nAChR was one of the first self-proteins associated with a defined autoimmune disease that was found to be expressed on thymic stromal populations. The studies described herein represent our efforts to determine how this "promiscuous" autoantigen expression may be involved in the immunopathogenesis of MG. We review our work, characterizing the expression of the nAChR alpha subunit in the thymus, and advance a hypothesis and experimental model, which explore how intrathymic expression of this autoantigen may contribute to the immunopathogenesis of this autoimmune disease.

Implication of double-stranded RNA signaling in the etiology of autoimmune myasthenia gravis

OBJECTIVE

Myasthenia gravis (MG) is an autoimmune disease mediated mainly by anti-acetylcholine receptor (AChR) antibodies. The thymus plays a primary role in MG pathogenesis. As we recently showed an inflammatory and antiviral signature in MG thymuses, we investigated whether pathogen-sensing molecules could contribute to an anti-AChR response.

METHODS

We studied the effects of toll-like receptor agonists on the expression of α-AChR and various tissue-specific antigens (TSAs) in human thymic epithelial cell (TEC) cultures. As polyinosinic-polycytidylic acid (poly[I:C]), which mimics double-stranded RNA (dsRNA), stimulated specifically α-AChR expression, the signaling pathways involved were investigated. In parallel, we analyzed the expression of dsRNA-signaling components in the thymus of MG patients, and the relevance of our data was investigated in vivo in poly(I:C)-injected mice.

RESULTS

We demonstrate that dsRNA signaling induced by poly(I:C) specifically triggers the overexpression of α-AChR in TECs and not of other TSAs. A poly(I:C) effect was also observed on MG TECs. This induction is mediated through toll-like receptor 3 (TLR3) and protein kinase R (PKR), and by the release of interferon (IFN)-β. In parallel, human MG thymuses also display an overexpression of TLR3, PKR, and IFN-β. In addition, poly(I:C) injections specifically increase thymic expression of α-AChR in wild-type mice, but not in IFN-I receptor knockout mice. These injections also lead to an anti-AChR autoimmune response characterized by a significant production of serum anti-AChR antibodies and a specific proliferation of B cells.

INTERPRETATION

Because anti-AChR antibodies are highly specific for MG and are pathogenic, dsRNA-signaling activation could contribute to the etiology of MG.

Targeting the fetal acetylcholine receptor in rhabdomyosarcoma

INTRODUCTION

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of childhood and adolescence. Recent efforts to enhance overall survival of patients with clinically advanced RMS have failed and there is a demand for conceptually novel treatments. Immune therapeutic options targeting the fetal nicotinic acetylcholine receptor (fnAChR), which is broadly expressed on RMS, are novel approaches to overcome the therapeutic resistance of RMS. Expression of the fnAChR is restricted to developing fetal muscles, some apparently dispensable ocular muscle fibers and thymic myoid cells. Therefore, after-birth fnAChR is a tumor-associated and almost tumor-specific antigen on RMS cells.

AREAS COVERED

This review gives an overview on nAChR function and expression pattern in RMS tumor cells, and deals with the immunological significance of fnAChR-expressing cells, including the risk of anti-nAChR autoimmunity as a potential side effect of fnAChR-directed immunotherapies. The article also addresses the advantages and disadvantages of vaccination strategies, immunotoxins and chimeric T cells targeting the fnAChR.

EXPERT OPINION

Finally, we suggest technical and biological strategies to improve the available immunotherapeutic tools including increasing the in vivo expression of the target fnAChR on RMS cells.

Variable Resistance of RMS to Interferon γ Signaling

Aims. Chimeric T cells directed to the γ-subunit of the fetal acetylcholine receptor (fAChR) produce large amounts of interferon-γ (IFNγ) on coculture with fAChR-expressing rhabdomyosarcoma (RMS) cells prior to RMS cell death. The aim of this study was to elucidate whether IFNγ blocks proliferation and survival of RMS cells and modulates expression of genes with relevance for cytotoxicity of chimeric T cells. Methods. Expression levels of IFNγ receptor (IFNGR), AChR, MHCI, MHCII, and CIITA (class II transactivator) by RMS were checked by flow cytometry, qRT-PCR, and western blot. Proliferation and cell survival were investigated by annexin V and propidium iodide staining and MTT (thiazolyl-blue-tetrazolium-bromide) assay. Key phosphorylation and binding sites of IFNGRs were checked by DNA sequencing. Results. IFNγ treatment blocked proliferation in 3 of 6 RMS cell lines, but reduced survival in only one. IFNGR was expressed at levels comparable to controls and binding sites for JAK and STAT1 were intact. Induction of several target genes (e.g., AChR, MHCI, and MHCII) by IFNγ was detected on the RNA level but not protein level. Conclusions. IFNγ does not significantly contribute to the killing of RMS cells by fAChR directed chimeric T cells. Signalling downstream of the IFNR receptor, including the posttranscriptional level, is impaired in most RMS cell lines.