Distribution of LATS activity in immunoglobulin G subclass

The immunological character of LATS was examined by affinity chromatography on Anti-IgG, Anti-Fab, Anti-Fc and Staphylococcal Protein A bound Sepharose. By affinity chromatography on Anti-IgG, Anti-Fab and Anti-Fc bound Sepharose, it is possible to separate LATS-immunoglobulin from LATS positive serum without loss of activity. Affinity chromatography on Protein A bound Sepharose is useful for obtaining further purified LATS-immunoglobulin. By this method, it is possible to separate IgG molecules of the subclasses IgG(1), IgG(2) and IgG(4) with high LATS activity. LATS activity was not found in the IgG(3) fraction. When IgG(1) fraction was purified from the fraction containing the 3 subclasses of IgG(1), IgG(2) and IgG(4), about 85% of total protein was found in IgG(1). However, specific activity per protein of LATS in IgG(1) fraction did not change remarkably. After papain hydrolysis the thyroid stimulating activity of LATS-immunoglobulin was located in Fab fraction of these 3 subclasses of IgG(1), IgG(2) and IgG(4), and especially in IgG(1). The Fab fraction presents a short acting type of thyroid stimulating activity. These data indicate that LATS activity is mainly distributed in the Fab fragment of IgG(1).