Background and Aims

Myasthenia gravis (MG) is a rare neuromuscular disease due to autoantibodies against the acetylcholine receptor (AChR). Thymic abnormalities are associated with MG such as ectopic germinal center development with B cells producing anti-AChR antibodies. The MG thymus is characterized by the overexpression of interferon (IFN)-β and IFN-I induced genes (ISGs). IFN-β orchestrates thymic changes associated with MG and favors the autoimmune reaction against α-AChR. An IFN-I signature is observed in periphery in other autoimmune diseases such as SLE or dermatomyositis. Our objective was to search for an IFN-I signature in periphery in MG patients.

Methods

Serum and PBMCs were collected from early-onset MG (EOMG) patients and age-matched healthy donors. The expression of IFN-α, IFN-β and six ISGs have been measured by RT-qPCR in PBMCs. The serum levels of IFN-α and IFN-β have been measured by Simoa and ELISA.

Results

In PBMCs, no increased expression of IFN-α, IFN-β or of ISGs, except RASD2, were observed in MG either in patients treated or not with corticosteroids or in patients thymectomized or not.

In the serum, no increased expression of IFN-α and IFN-I were observed in MG patients even when patients were stratified according to the severity of the disease or to their treatments (corticosteroids, thymectomy).

Conclusions

Altogether, these results showed that there is no IFN-I signature in PBMCs or in the serum of EOMG patients. The IFN-I signature is confined to the thymus with no apparent release in the periphery.