Epitopes expressed in myasthenia gravis (MG) thymomas are not recognized by patients' T cells or autoantibodies.

Most thymic epithelial tumours that associate with MG express an epitope that resembles the sequence alpha373-380 from the cytoplasmic loop of the acetylcholine receptor (AChR). It has been proposed that sensitization to this linear epitope initiates autoimmunity to the AChR in thymoma-associated MG. We therefore tested whether MG/thymoma patients have T cell responses or antibodies to this region of the AChR. We found no significant recognition of the alpha309-417 region by their thymoma or peripheral blood T cells, or by their serum anti-AChR antibodies. Instead, the T cell epitopes that were recognized, like the previously characterized B cell epitopes, were in the extracellular AChR domain.