| Abstract: | Binding of immunoglobulin G (IgG) to Triton-solubilized fat cell membranes crosslinked with 125I-TSH was studied by an indirect immunoprecipitation method. Guinea pig fat cell membranes (FCM) containing TSH receptors with an association constant of 1.92 X 10(9) M-1 were first reacted with 125I-TSH, then treated with a crosslinker, dissuccinimidyl suberate. The dissociation of 125I-TSH from the crosslinked 125I-TSH-FCM complexes due to the addition of 100 mU/ml unlabeled TSH was 9.0%, while it was 33% without the treatment. To the Triton-solubilized FCM crosslinked with 125I-TSH, 50 micrograms each of IgG from 20 normal controls, 20 patients with Graves' disease and 20 with Hashimoto's disease was added and precipitation was effected by adding anti-human IgG. In patients with Graves' disease, 125I-TSH-FCM complexes immunoprecipitated ranged from 1.10 to 4.18% with an average of 2.4 +/- 0.99 (S. D.) % which was significantly higher than those in normal controls (1.6 +/- 0.29%). The values in the patients with Hashimoto's disease averaged 1.7 +/- 0.53 (S. D.) which did not differ significantly from those of controls. The value did not correlate with either TSH-binding inhibiting activities or titers of anti-microsomal antibodies. These data suggest the presence of TSH-receptor antibodies which react with antigens other than TSH-binding sites in the patients with Graves' disease. |
