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

Authors
P. Cufi, N. Dragin, J. M. Weiss, P. Martinez-Martinez, M. H. De Baets, R. Roussin et al.

Lab
CNRS, Paris, France.

Journal
Annals of Neurology

Abstract
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.

BIOSEB Instruments Used:
Grip strength test (BIO-GS3)