B cell and autoantibody repertoire in a pair of monozygotic twins discordant for myasthenia gravis.

A pair of identical twins, 47 years of age, who have been discordant for myasthenia gravis for 15 years were studied with regard to clinical status, neuromuscular function, and presence and properties of myasthenia specific autoantibodies. The autoantibody repertoire was tested in serum, as produced by peripheral lymphocytes in culture and as revealed by B cell lines. The healthy twin had no clinical signs of myasthenia and no signs of impaired neuromuscular function on electrophysiological tests. The autoantibody repertoire and the avidity of the anti-receptor antibodies were similar in both individuals. Epstein-Barr virus transformation of peripheral lymphocytes revealed a higher incidence of B cells committed to make autoantibodies in the healthy twin than in her myasthenic sister.