Autoimmune myasthenia gravis (MG) is a neuromuscular disorder characterized by a defective transmission of nerve impulses to muscles. This defect is caused by an autoimmune attack against components of the neuromuscular junction, mainly against the acetylcholinecholine receptor (AChR), but also against the muscle-specific kinase (MuSK) and the low-density lipoprotein-related protein 4 (LRP4). Clinical characteristics of MG are fluctuating fatigable muscle weaknesses but clinical subgroups of MG patients are proposed depending on the type of autoantibodies, the muscles targeted (ocular forms versus generalized forms), the age at onset and also the thymic physiopathology. If the neuromuscular junction is the target of the autoantibody attack, the thymus is involved in the disease. First, it plays a central role in the education of T cells to shape the immune repertoire and avoid the escape of autoreactive T cells. In addition, in AChR-MG patients, histological abnormalities are also observed with either a follicular hyperplasia or a thymoma. MG is a chronic disease and patients need treatments for the rest of their lives. Current treatments include mainly cholinesterase inhibitors combined with corticosteroids, but also, if necessary, immunosuppressors, broad anti-immune therapies and B-cell depletion therapy. Thymectomy is also part of the standard therapeutic treatment for AChR-MG patients with or without a thymoma.

The etiological mechanisms leading to MG symptoms are not yet completely defined and are still a matter of strong interest in the scientific community. It is well-admitted that genetic predispositions exist in MG patients. However, additional events/changes occur that lead to disease onset. Recent investigations have underlined the role of epigenetic changes, such as DNA methylation or miRNA expression in autoimmune processes. Sexual hormones can also intervene and favor autoimmunity in women. Environmental factors are also candidates for driving/perpetuating autoimmunity, such as pathogen infection, endocrinal disruptors, microbiota changes…

The production of autoantibodies is dependent upon B cells but also of interactions with CD4+ T cells. Th1, Th2 and more recently Th17 cells have been involved in MG pathogenic mechanisms. T follicular helper cells are also important for providing help to B cells for ectopic germinal center development in the thymus. In addition, defects are observed regarding the functionality of regulatory T cells and B cells in MG patients. However, it is not clearly defined if this immune imbalance pre-exists in susceptible MG patients before the onset of the disease or if this is a consequence of the inflammation induced by a triggering event.

This Research Topic aims to discuss recent discoveries in myasthenia gravis. We welcome the submission of reviews and original research articles covering, but not limited to, the following themes:

• The importance of epigenetic changes in immune cells
• The impact of environmental factors
• The immune unbalance in the onset or the chronicity of the disease
• The consequence of the autoantibody attack
• The identification of serum biomarkers
• New therapeutic approaches

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