Phenotypic and Functional Characterization

A study of cell surface phenotypes of PBL of myasthenia gravis (MG) patients showed that their T cells had a significantly higher percentage of 4B4+ T cells (the helper/inducer subset) than ageand sex-matched controls. The PBL of MG patients proliferated significantly higher than those of normal subjects (NS) in response to the purified a chain of the acetylcholine receptor (AChR). Anti-AChR antibody was present in sera of 88% of MG and none of the NS. The PBL B cells from MG only, when cultured with autologous T cells and stimulated with either pokeweed mitogen (69%), or AChR-a chain (38%), secreted antibody to AChR-a chain, whereas T and B cells alone secreted no antibody. T cells from PBL ofMG patients were more readily cloned than T cells of NS, by limiting dilution, in the presence of recombinant IL-2 and in the absence of AChR-a chain. About 50% ofT cell clones from MG patients, compared to none from NS, proliferated to AChR-a chain. This response was HLADR restricted. MG T cell clones did not display significant cytotoxic activity, as compared to control T cell clones. Our results indicate that in MG, 4B4+ regulatory T cells play their role in the pathogenesis of MG, not by cytotoxicity, but more likely by their ability to stimulate specific antibody production by B cells. (J. Clin. Invest. 1990. 86:2099-2108.)