title: Choice of immunoglobulin G purification method in assays for antibodies to the thyrotropin receptor.
abstract: Activity of autoantibodies to the thyrotropin receptor in the serum of patients with active Graves's disease was compared when the patients' IgG was purified by three different procedures: ammonium sulfate precipitation (I), a modified batch diethylaminoethyl cellulose method (II), and affinity chromatography on Protein A-Sepharose CL-4B (III). IgG extracted by I was significantly less potent in inhibiting binding of 125I-labeled thyroid membranes than that prepared by either II or III, and was significantly less effective than II in stimulating adenyl cyclase activity in thyroid membrane. Thyroglobulin, a serum protein whose concentration is increased in patients with various thyroid diseases, was coprecipitated in amounts sufficient to significantly inhibit binding only when method I was used, but not with either of the other two procedures. Evidently method I is inferior to either of the other two when used for purification of autoantibodies to the thyrotropin receptor. Method II used in this study, being faster and more economical than I and of equivalent efficacy, is a feasible alternative method for clinical use.
mesh_terms: D000645:Ammonium Sulfate; D000906:Antibodies / Q000302:isolation & purification*; D001323:Autoantibodies / Q000302:isolation & purification; D002846:Chromatography, Affinity; D002848:Chromatography, DEAE-Cellulose; D006111:Graves Disease / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis / Q000302:isolation & purification*; D018828:Immunoglobulins, Thyroid-Stimulating; D011989:Receptors, Thyrotropin / Q000276:immunology*; D013205:Staphylococcal Protein A; D013961:Thyroid Gland / Q000378:metabolism; D013972:Thyrotropin / Q000037:antagonists & inhibitors
chemical_list: D000906:Antibodies; D001323:Autoantibodies; D007074:Immunoglobulin G; D018828:Immunoglobulins, Thyroid-Stimulating; D011989:Receptors, Thyrotropin; D013205:Staphylococcal Protein A; D013972:Thyrotropin; D000645:Ammonium Sulfate