Demonstration of the production of the long acting thyroid stimulator (LATS) by peripheral lymphocytes cultured in vitro.

Peripheral lymphocytes from thyrotoxic patients with detectable plasma LATS were cultured for 6 days with phytohaemagglutinin (PHA). LATS was found in the culture medium in seven of eleven cultures with PHA, but on only one occasion without PHA, and only once in the material extracted from the lymphocytes by freezing and thawing. LATS was not detected in the medium in which cells from normal people were cultured or when medium was incubated in the absence of cells. The LATS activity was neutralized by anti-IgG serum. That the LATS was produced by the cells during culture rather than released as antibody preformed was confirmed by the absence of LATS in cultures of the cells frozen at the beginning of incubation. These findings provide further evidence that LATS is an immunoglobulin thereby strengthening the hypothesis that Graves' disease is an autoimmune disorder.