Inhibition of long-acting thyroid stimulator by thyroid particulate fractions.

The long-acting thyroid stimulator (LATS), found uniquely in the serum of patients with Graves' disease, is closely associated with the immunoglobulin G (IgG) proteins of serum and is removed from serum by antibody to human IgG (2, 3). Since some IgG molecules function as antibodies, it seems possible that LATS is also an antibody. This possibility would be strengthened if LATS could be demonstrated to react specifically with an antigen. In an effort to demonstrate such a reaction we incubated serum containing LATS with insoluble fractions of thyroid tissue and evaluated the effects of this incubation by measuring LATS in the serum freed of suspended material by centrifugation. These experiments represent a confirmation and extension of studies reported by Kriss, Pleshakov, and Chien, in which they showed inhibition of LATS activity by slices and homogenates of dog and human thyroid (3). We also explored the specificity, stability, sensitivity, and, to some extent, the nature of the interaction between thyroid tissue and LATS. Methods