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Research Article Free access | 10.1172/JCI116024

Myasthenia gravis. CD4+ T epitopes on the embryonic gamma subunit of human muscle acetylcholine receptor.

M P Protti, A A Manfredi, X D Wu, L Moiola, M W Dalton, J F Howard Jr, and B M Conti-Tronconi

Department of Biochemistry, College of Biological Sciences, University of Minnesota, St. Paul 55108.

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Department of Biochemistry, College of Biological Sciences, University of Minnesota, St. Paul 55108.

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Department of Biochemistry, College of Biological Sciences, University of Minnesota, St. Paul 55108.

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Department of Biochemistry, College of Biological Sciences, University of Minnesota, St. Paul 55108.

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Department of Biochemistry, College of Biological Sciences, University of Minnesota, St. Paul 55108.

Find articles by Dalton, M. in: PubMed | Google Scholar

Department of Biochemistry, College of Biological Sciences, University of Minnesota, St. Paul 55108.

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Department of Biochemistry, College of Biological Sciences, University of Minnesota, St. Paul 55108.

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Published October 1, 1992 - More info

Published in Volume 90, Issue 4 on October 1, 1992
J Clin Invest. 1992;90(4):1558–1567. https://doi.org/10.1172/JCI116024.
© 1992 The American Society for Clinical Investigation
Published October 1, 1992 - Version history
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Abstract

In myasthenia gravis (MG) an autoimmune response against muscle acetylcholine receptor (AChR) occurs. Embryonic muscle AChR contains a gamma subunit, substituted in adult muscle by a homologous epsilon subunit. Antibodies and CD4+ cells specific for embryonic AChR have been demonstrated in MG patients. We identified sequence segments of the human gamma subunit forming epitopes recognized by four embryonic AChR-specific CD4+ T cell lines, propagated from MG patients' blood by stimulation with synthetic peptides corresponding to the human gamma subunit sequence. Each line had an individual epitope repertoire, but two 20-residue sequence regions were recognized by three lines of different HLA haplotype. Most T epitope sequences were highly diverged between the gamma and the other AChR subunits, confirming the specificity of the T cells for embryonic AChR. These T cells may have been sensitized against AChR expressed by a tissue other than innervated skeletal muscle, possibly the thymus, which expresses an embryonic muscle AChR-like protein, containing a gamma subunit. Several sequence segments forming T epitopes are similar to regions of microbial and/or mammalian proteins unrelated to the AChR. These findings are consistent with the possibility that T cell cross-reactivity between unrelated proteins ("molecular mimicry"), proposed as a cause of autoimmune responses, is not a rare event.

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