Methods for separation of long-acting thyroid stimulator (LATS) from sera containing LATS and TSH

Methods were devised for separation of long-acting thyroid-stimulator (LATS) from TSH in serum containing both thyroid stimulators by using Rivanol, concanavalin A (con A), or staphylococcal protein A. When 3-5 volumes of 0.5% Rivanol solution were mixed to serum containing TSH or LATS activity, LATS activity remained mainly with IgG in the supernatant fraction. On the contrary, TSH activity was precipitated. When 10 mg con A was added to 1 ml test serum, almost all TSH activity was precipitated, but LATS activity remained in the supernatant fraction, which consisted mainly of IgG and albumin. Almost all LATS activity and part of the TSH activity were precipitated by addition of more than 7.5% polyethylene glycol (PEG), which was therefore not useful for separation of the stimulators in serum. Affinity chromatography on staphylococcal protein A-Sepharose was also found to separate the two thyroid stimulators in serum. By this method LATS-immunoglobulin bound to the protein A column, but no binding of the biologic and immunologic activity of TSH was observed. The protein A method seems the most useful of these four methods for complete separation of both stimulators.