In vitro anti-acetylcholine receptor antibody synthesis by myasthenia gravis patient lymphocytes: correlations with thymic histology and thymic epithelial-cell interactions.

In vitro anti-acetylcholine receptor antibody (anti-AChR Ab) production by peripheral blood lymphocytes (PBL) and thymic lymphocytes was investigated in 52 patients with myasthenia gravis (MG). There was a positive correlation between in vitro anti-AChR Ab synthesis and in vivo titers. A relationship between the rates of synthesis by PBL and histological abnormalities of the thymus was also observed. Patients with hyperplastic thymus tended to produce the largest amounts in vitro, while those with an involuted thymus produced little or none. Production in thymoma patients is likely to correlate with the histological nature of the thymus associated with the tumor. In vitro Ab synthesis was modulated by the depletion of a cell subset for half of the patients tested. Finally, anti-AChR Ab production by thymocytes but not by PBL is enhanced by the addition of autologous or allogeneic thymic epithelial cells, suggesting a possible role of thymic epithelial cells in the autosensitization against AChR occurring in the thymus.