DISTRIBUTION OF LONG-ACTING THYROID STIMULATORAMONG GAMMAG-IMMUNOGLOBULINS

γG-globulin prepared from long-acting thyroid stimulator (LATS) serum using (NH4)2SO4 precipitation and DEAE-cellulose chromatography sometimes was found to have a lower specific LATS activity than a dilution of the original serum containing a comparable amount of γG-globulin. The apparent loss of activity varied between sera from different patients and was found to be associated with the euglobulins. Gel filtration of euglobulins on Sephadex G200 indicated that the activity was only associated with '7-S' protein. Chromatography of sera on DEAE-Sephadex resolved their LATS activity into two zones. One zone consisted entirely of electrophoretically slow γG-globulin, while the other contained several serum proteins including electrophoretically fast γG-globulin. The distribution of LATS activity between these two zones and within each zone varied with individual sera. γG-globulin devoid of LATS activity was isolated from three of the sera studied. The LATS activity of both zones could be absorbed by and partially eluted from human thyroid homogenates. Precipitation of euglobulins prior to chromatography showed that some LATS activity was removed from both zones. The activity of the soluble proteins, however, was limited to the electrophoretically slow zone. © 1969.