Immunoglobulin synthesis in vitro by human thymus: comparison of myasthenia gravis and normal thymus.

Immunoglobulin synthesis measured in incubated thymus tissue by the incorporation of [C]amino acids has been studied in four thymus glands from patients with myasthenia gravis and in eight normal thymus glands from patients undergoing open heart surgery. Parallel studies have been carried out with one normal human spleen and two lymph nodes. Thymus tissues from patients with myasthenia gravis incorporated an average of twice as much radioactivity into soluble protein on a wet weight basis as normal thymus tissues. On the same basis, they synthesized approximately six times as much immunoglobulin as the normal thymus, emphasizing the association of an abnormal immune response in the thymus with this disease. Comparison of incorporation of [C]amino acids into immunoglobulin showed that on a wet weight basis the normal lymph nodes studied synthesized a mean of twenty-five times, and the normal spleen, six times as much immunoglobulin as the normal thymus. Thus, these studies establish that the normal as well as the hyperplastic thymus gland shares with peripheral lymphoid tissue the capacity to produce immunoglobulin. Preliminary studies of the antibody specificity of a purified fraction of [C]IgG from myasthenia gravis and normal thymus have shown no reactivity of thymic IgG with normal human thymus or muscle by radioautographic and immuno-fluorescent techniques.