Acetylcholine receptor antibody-producing cells in thymus and lymph nodes in myasthenia gravis

Eleven patients with myasthenia gravis (5 with thymoma) were studied and spontaneous production of antibody to acetylcholine receptor (AChR) in vitro was found by thymus cells in 10 (and in all 5 with thymoma) and by lymph node cells in 8 (and in 3 with thymoma). The rate of AChR antibody production by thymus cells was greater than that by lymph node cells (10.7 ± 11.6 and 1.4 ± 1.5 fmol/10 6 cells/week, respectively, mean ± SD, P < 0.05 by paired t test), although the B-cell population was always smaller in the thymus than in the lymph nodes (9.5 ± 9.4 and 31 ± 12.7%, P < 0.001), suggesting the principal role of the thymus in AChR antibody production. It is suggested that lymph nodes can be one of the main sites of AChR antibody production in myasthenia gravis but the antibody-producing cells may originate in the thymus.