[B cell population and its autoimmune activity in the thymus of patients associated with myasthenia gravis].

Immunohistochemical studies using antibodies to B lymphocyte and to immunoglobulin G bearing cell were carried out for resected thymus-specimens of 10 patients associated with myasthenia gravis. In each case, abundant B cells (L26 positive cell) resided in the follicles and the medulla of thymus, especially, were congregated in the follicles developing germinal center and around Hassall's corpuscles. Amount of B cell population was various among each case regardless of type of myasthenia gravis or age. B cells were greatly increased in the thymus of patients with values of anti-acetylcholine receptor antibody titers over 100 nmol/l. Although numerous B cells were present in the thymus of these patients, IgG bearing cells were extremely rare. In the most cases, B cells lacked IgG expression. From the results, numerous B cells pre-activating autoimmune antibody production were accumulated in the thymus of patients associated with myasthenia gravis.