Shifting of the blood T:B lymphocyte ratio in myasthenia gravis patients after thymectomy.

The immunologic role of thymus in human adults is still unclear, in a high percentage of patients with myasthenia gravis, improvement of the disease follows thymectomy. The biologic basis of this phenomenon is also unknown. We found that patients thymectomized for more than 9 months have a low percentage of T cells (mean 34 percent). The mean T cell percentage in control myasthenia gravis patients is 52 percent. Patients thymectomized for more than 18 and 24 months exhibit values of T cell percentage not lower than those of patients thymectomized for more than 9 months. Our results may be interpreted according to a humoral action of the thymus in regulating the percentage of T lymphocytes.