Thymic lymphoepitheliomas and skeletal muscle expressing common antigen(s)

Rabbit antiserum to a citric acid extract of human skeletal muscle (CA) stained epithelial thymoma cells as well as skeletal muscle. Thymomas from two myasthenia gravis (MG) patients showing no circulating anti-CA antibodies prior to thymectomy were also stained by the antiserum. Thus, in these patients as well, the thymoma and skeletal muscle possess common antigens. The rabbit and the human antibodies most probably reacted with different antigens, apparently located close to each other in the cell membrane. The reason why anti-CA antibodies cannot be detected in serum from a few MG patients with a thymoma may be that the thymoma-associated antigen is not present in vivo in these cases, or that an inhibiting factor blocks the antibody synthesis. Both patients developed anti-CA antibodies post-operatively, which favours the latter explanation.