Concentration-dependent regulation of thyrotropin receptor function by thyroid-stimulating antibody.
Thyrotropin receptor (TSHR) Ab's of the stimulating variety are the cause of hyperthyroid Graves disease. MS-1 is a hamster mAb with TSHR-stimulating activity. To examine the in vivo biological activity of MS-1, mice were treated with purified MS-1 intraperitoneally and the thyroid response evaluated. MS-1 induced a dose-dependent increase in serum thyroxine (T4), with a maximum effect after 10 proportional, variant g of MS-1 was administered. MS-1-secreting hybridoma cells were then transferred into the peritoneum of nude mice to study chronic thyroid stimulation. Serum MS-1 levels detected after 2 weeks were approximately 10-50 proportional, variant g/ml, and the serum TSH was suppressed in all animals. Serum triiodothyronine levels were elevated, but only in animals with low serum MS-1 concentrations. In addition, there was a negative correlation between serum T4 and the serum MS-1 concentrations. These in vivo studies suggested a partial TSHR inactivation induced by excessive stimulation by MS-1. We confirmed this inactivation by demonstrating MS-1 modulation of TSHR function in vitro as evidenced by downregulation and desensitization of the TSHR at concentrations of MS-1 achieved in the in vivo studies. Thus, inactivation of the TSHR by stimulating TSHR autoantibodies (TSHR-Ab's) in Graves disease patients may provide a functional explanation for the poor correlation between thyroid function and serum TSHR-Ab concentrations.
Ando
Takao
T
Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine, Mount Sinai School of Medicine, New York, New York 10029, USA. takao.ando@mssm.edu
Latif
Rauf
R
Davies
Terry F
TF
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004306:Dose-Response Relationship, Immunologic; D018828:Immunoglobulins, Thyroid-Stimulating / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D011989:Receptors, Thyrotropin / Q000378:metabolism*; D013961:Thyroid Gland / Q000276:immunology / Q000378:metabolism
D018828:Immunoglobulins, Thyroid-Stimulating; D011989:Receptors, Thyrotropin