Table of Contents Author Guidelines Submit a Manuscript
Developmental Immunology
Volume 2, Issue 2, Pages 77-84
http://dx.doi.org/10.1155/1992/86853

A Striational Muscle Antigen and Myasthenia Gravis-Associated Thymomas Share an Acetylcholine-Receptor Epitope

1lnstitute of Pathology, University of Wüzburg, Wüzburg 8700, Germany
2Pathologisches Institut der Universität, Josef Schneider Str. 2, Würzburg 8700, Germany
3Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
4Helenic Pasteur Institute, Athens, Germany
5Department of Neurology, University of Waüzburg,, Germany
6Department of Neurology, University of Mainz, Germany

Copyright © 1992 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The coincidence of autoantibodies against the acetylcholine receptor (AChR) and muscle striational antigens (SA) is a characteristic finding in thymoma-associated myasthenia gravis (MG), but their origins are still unresolved. Some common muscle antigens that were shown to be targets of anti-SA autoantibodies in thymoma-associated MG have also been detected in normal or neoplastic thymic epithelial cells, suggesting that the release of (eventually altered) antigens from the thymic tumors could elicit SA autoimmunity. In contrast to this model, we report here that titin, which is a recently reported target of SA autoimmunity, is not expressed in thymomas. In addition, we show that skeletal muscle type-II fibers exhibit a striational immunoreactivity with monoclonal antibody mAb155, which was previously identified to label a very immunogenic cytoplasmic epitope of the AChR and neoplastic epithelial cells of MGassociated thymomas. We conclude from these findings that titin autoimmunity in thymoma-associated MG is either due to a molecular mimicry mechanism involving tumor antigens (other than titin) or is a secondary phenomenon following release of titin from muscle. Based on the common immunoreactivity of the AChR, a striational antigen and thymoma, we suggest as the pathogenetic mechanism of thymoma-associated MGa "circulus vitiosus" in which SA autoimmunity could help maintain the AChR autoimmunity that is primarily elicited by the thymomas.