title: Simultaneous assay of thyroid adenylate cyclase- and growth-stimulating antibodies using FRTL-5 cells. Evidence suggesting their identity in patients with Graves' disease.
abstract: The relationship between thyroid growth-stimulating antibodies (TGSAb) and thyroid adenylate cyclase-stimulating antibodies (TSAb) in patients with Graves' disease is still a matter of controversy. To investigate this problem, we have developed an assay for the simultaneous measurement of TSAb and TGSAb using FRTL-5 cells. TSAb was detected by its ability to stimulate iodide (I-) uptake and TGSAb by the 3H-thymidine ([3H]-Tdr) incorporation assay. Thirty-four immunoglobulin G (IgG) preparations from patients with active Graves' disease were selected from a previous series in order to include both TSAb-negative IgGs (n = 9) and TSAb-positive IgGs (n = 25) by the cAMP stimulation assay, with a wide range of stimulatory activity. With one exception, the TSAb-positive IgGs produced a significant stimulation of I- uptake; 20 of them were also TGSAb-positive. The nine IgGs negative in the cAMP assay, were also negative in the I-uptake and the [3H]-Tdr incorporation assays. The majority of samples had a similar potency in the two assays and a significant positive correlation was found (r = 0.76; P less than 0.001). Two IgGs previously shown to inhibit TSH-stimulated adenylate cyclase in FRTL-5 cells produced an almost complete inhibition (80-90%) of both TSH- and Graves' IgG-stimulated I- uptake and [3H]-Tdr incorporation. In conclusion, using a simultaneous assay for thyroid growth and adenylate cyclase stimulation, TGSAb in Graves' patients were found only in TSAb-positive IgGs; both Graves' IgG-stimulated activities were inhibited by antibodies blocking the TSH-dependent adenylate cyclase stimulation. Our data strongly suggest that the same antibody may be responsible for both goitre and thyroid hyperfunction of Graves' disease.
authors.affiliation: Istituto di Metodologia Clinica e Medicina del Lavoro, Università di Pisa, Tirrenia, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Marcocci
authors.forename: P
authors.initials: P
authors.lastname: Vitti
authors.forename: G
authors.initials: G
authors.lastname: Lopez
authors.forename: F
authors.initials: F
authors.lastname: Santini
authors.forename: C
authors.initials: C
authors.lastname: Mammoli
authors.forename: G F
authors.initials: GF
authors.lastname: Fenzi
authors.forename: A
authors.initials: A
authors.lastname: Pinchera
mesh_terms: D000262:Adenylyl Cyclases / Q000032:analysis*; D001323:Autoantibodies / Q000032:analysis*; D001681:Biological Assay / Q000379:methods; D002455:Cell Division; D002460:Cell Line; D005260:Female; D006111:Graves Disease / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis* / Q000276:immunology; D018828:Immunoglobulins, Thyroid-Stimulating; D007455:Iodine / Q000378:metabolism; D008297:Male; D013961:Thyroid Gland / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D007074:Immunoglobulin G; D018828:Immunoglobulins, Thyroid-Stimulating; D007455:Iodine; D000262:Adenylyl Cyclases