title: TSH receptor antibodies do not alter the function of gonadotropin receptors stably expressed in eukaryotic cells.
abstract: OBJECTIVE
  TSH receptor (TSHr) mediates the activating action of TSH on the thyroid gland resulting in the growth and proliferation of thyrocytes and thyroid hormone production. TSHr is a major autoantigen in Graves' disease (GD) and is the target for TSHr antibodies. In GD, thyroid-stimulating antibodies (TSAb) are competitive agonists of TSH. In atrophic thyroiditis (AT), thyroid-stimulating blocking antibodies (TSHBAb) are TSH antagonists. The TSHr together with the LH receptor (LHr) and FSH receptor (FSHr) are G-protein-coupled receptors with considerable amino acid homologies in the extracellular domain. We studied the cross-reactivity of the antibodies measured in sera from patients with GD or AT on the LHr and FSHr function.
  
  
  METHODS
  We tested the activity of TSAb and TSHBAb in cell lines expressing the LHr and the FSHr. To this purpose a pSVL-FSHr construct was transfected in CHO cells and one clone was used.
  
  
  RESULTS
  Twenty-eight sera from patients with GD and four from patients with AT, known to contain TSHr antibodies measured with a radioreceptor assay, were selected. TSAb and TSHBAb activities were measured in CHO cells expressing the TSHr (CHO-TSHr). TSAb and TSHBAb were then tested with the cell lines expressing the LHr and the FSHr for their ability to elicit cAMP accumulation or inhibit FSH/LH-induced cAMP production. None of the TSAb identified was able to stimulate cAMP increase in CHO-LHr or CHO-FSHr. Similarly, none of the TSHBAb was able to block the cAMP response induced by FSH or LH in the respective cell lines.
  
  
  CONCLUSIONS
  Our results confirm the notion of the organ-specific nature of the TSHr antibodies.
authors.affiliation: Dipartimento di Endocrinologia e Metabolismo, Universita degli Studi di Pisa, Via Paradisa 2, 56124, Cisanello, Pisa, Italy. mtonacchera@hotmail.com
authors.forename: Massimo
authors.initials: M
authors.lastname: Tonacchera
authors.forename: Eleonora
authors.initials: E
authors.lastname: Ferrarini
authors.forename: Antonio
authors.initials: A
authors.lastname: Dimida
authors.forename: Patrizia
authors.initials: P
authors.lastname: Agretti
authors.forename: Giuseppina
authors.initials: G
authors.lastname: De Marco
authors.forename: Melissa
authors.initials: M
authors.lastname: De Servi
authors.forename: Luca
authors.initials: L
authors.lastname: Chiovato
authors.forename: Filomena
authors.initials: F
authors.lastname: Cetani
authors.forename: Paolo
authors.initials: P
authors.lastname: Vitti
authors.forename: Aldo
authors.initials: A
authors.lastname: Pinchera
mesh_terms: D000818:Animals; D019138:Antibodies, Blocking / Q000276:immunology / Q000378:metabolism; D001323:Autoantibodies / Q000276:immunology* / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D003429:Cross Reactions / Q000276:immunology; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D006111:Graves Disease / Q000276:immunology / Q000378:metabolism; D006801:Humans; D018828:Immunoglobulins, Thyroid-Stimulating / Q000276:immunology* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011962:Receptors, FSH / Q000276:immunology / Q000378:metabolism; D011974:Receptors, LH / Q000276:immunology / Q000378:metabolism; D011989:Receptors, Thyrotropin / Q000276:immunology* / Q000378:metabolism; D013967:Thyroiditis, Autoimmune / Q000276:immunology / Q000378:metabolism*
chemical_list: D019138:Antibodies, Blocking; D001323:Autoantibodies; D018828:Immunoglobulins, Thyroid-Stimulating; D011962:Receptors, FSH; D011974:Receptors, LH; D011989:Receptors, Thyrotropin; C094372:thyrotropin-binding inhibitory immunoglobulin; D000242:Cyclic AMP