Myasthenia gravis patients, but not healthy subjects, recognize epitopes that are unique to the ɛ-subunit of the acetylcholine receptor

Myasthenia gravis (MG) is an autoimmune disease characterized by deficits in neuromuscular transmission due to antibody-mediated damage of the acetylcholine receptor (AChR). We examined the in vitro immune response of peripheral blood mononuclear cells isolated from MG patients (n=38) and healthy nonmyasthenic subjects (n=31) to epitopes on the α-, ɛ-, and γ-chains of the AChR. The ɛ- and γ-epitopes tested represent regions with little sequence homology to the α-chain, and little sequence homology between the ɛ- and γ-chains. No differences were observed in the immune response of MG patients and healthy subjects to any of the α-chain epitopes tested. Serial studies of the immune response to the α-peptides suggest that epitope spread does occur over time. Cells from MG patients were stimulated by the ɛ- and γ-chain peptides, although the response was weaker than that to the α-peptides. Cells from healthy subjects showed reactivity to γ-chain peptides only; none of the healthy subjects responded to the ɛ-chain peptides tested. Differences between the ɛ- and γ-chains may be important in the development of MG, because only MG patients respond to epitopes that are unique to the ɛ-subunit.