Depletion of helper/inducer T cells after thymectomy in myasthenic patients.

Using monoclonal anti-T-cell antibodies, we have studied peripheral blood T-cell subsets in 53 patients with myasthenia gravis before and after thymectomy (Tx). Before Tx, the mean OKT4/OKT8 ratio was higher in patients than in controls. Furthermore patients showed a high number of cells reacting simultaneously with the OKT4 and OKT8 antibodies. Shortly after surgery, the helper/suppressor ratio was increased in most of the patients, and the doubly reactive subset decreased to normal levels. However, 6 to 12 months after Tx the OKT4/OKT8 ratio was significantly decreased, particularly in patients showing clinical improvement. The percentage of total T cells was slightly but significantly reduced. A group of 14 patients studied more than 2 years after Tx presented very low OKT4/OKT8 ratios. Thymectomy in MG appears to lead to a gradual decrease of the T-helper subset which could contribute to its favorable effect on the course of the disease.