Study of the pathogenic mechanisms of autoimmune myasthenia gravis


Myasthenia gravis (MG) is an autoimmune disease caused by the presence of antibodies directed against components of the muscle membrane located at the neuromuscular junction. In the majority of cases, these are autoantibodies directed against the acetylcholine receptor (AChR). The origin of the autoimmune response is not known, but thymic abnormalities and defective regulation of the immune system certainly play a major role in patients with anti-AChR antibodies. It has thus been shown that environmental contaminants may be involved in the induction of myasthenia gravis via deregulation of pro-inflammatory Th17 lymphocytes via their AhR receptor. In the MG thymus, the balance of the couple composed of regulatory T lymphocytes (Treg) (anti-inflammatory) and Th17 lymphocytes plays an important role. Indeed, it has been suggested that the overexpression of cytokines IL-17 and IL-6 by Th17 could contribute to the maintenance of pathogenic inflammatory phenomena and to the production of autoantibodies.

Duration of Inovarion intervention

12 months


Scientific purposes

In this context, the project carried out aimed to better understand the pathophysiology of MG using preclinical experimental models of autoimmune myasthenia gravis. In particular, the involvement of the IL-17/IL-23 pathway in myasthenia gravis was analyzed. The ultimate goal of the work was to develop an innovative therapy to treat autoimmune myasthenia gravis that could be based on the use of monoclonal antibodies targeting the IL-17/IL-23 pathway.


Uncertainties, difficulties and technological complexities

The work undertaken presented the following technological and conceptual uncertainties, difficulties and constraints:

  • Effects of interactions between thymic epithelial cells (TECs) and CD4 lymphocytes on the IL-17/IL-23 axis: comparison of MG epithelial cells/healthy cells
  • Effects of interferons on the IL-17/IL-23 axis: comparison between MG cells/healthy cells
  • No immunohistochemical analysis of proteins involved in the equilibrium between the IL17/IL23 pathway and Treg cells in the thymus


Description of the work carried out

Characterization of the IL-17 / IL-23 pathway was carried out from thymic biopsies and on in vitro models using primary cultures of thymic epithelial cells (TECs) and / or lymphocytes (PBMC). A cytokine signature promoting the development of Th17 lymphocytes was thus found in the thymi of myasthenic patients. In addition, a pathogenic subgroup has been identified when this cell family is confronted with the cytokine TGFβ3. In addition, RT-QPCR analysis indicates that TGFβ3 is overexpressed in the thymi of myasthenic patients compared to thymi controls. This latter observation is also true for interleukin 23, whose expression is increased in myasthenic compared to control TECs. At the protein level, an immunohistochemistry analysis of thymic biopsies reveals an accumulation of IL-23 in the interlobular spaces and a significant increase in the level of expression of this cytokine by epithelial cells.

In order to determine whether increased secretion of IL-23 by myasthenic TECs can induce changes in the Treg and Th17 lymphocyte populations, CD4+ T cells controls were cultured with control or myasthenic TECs. Under these conditions, control TECs do not induce changes in the expression of Th17 lymphocyte signature markers (IL-17 and RORc), whereas the myasthenic TECs induce changes in the expression of these markers.

In order to identify the Th17 subpopulation that may be responsible for the inflammation observed in the MG thymus, thymic CD4 + cells were analyzed by flow cytometry. The results indicate an enrichment of Th17 in myasthenic thymi. In addition, the expression of podoplanin evaluated by RT-qPCR is higher in myasthenic thymi and TECs than in the control situation.


Main results

All the results obtained led to the writing of an original article entitled « Cultured Human Thymic-Derived Cells Display Medullary Thymic Epithelial Cell Phenotype and Functionality » by Villegas JA, Gradolatto A, Truffault F, Roussin R, Berrih-Aknin S, Le Panse R, Dragin N published in Frontiers in Immunology in 2018 (doi: 10.3389/fimmu.2018.01663. eCollection 2018; PMID: 30083154)