Characterization of a bioeffective monoclonal antibody against thyrotropin beta-subunit.
To describe a region of the TSH molecule participating in binding to receptor, a monoclonal antibody specific for a TSH epitope shared by beta-subunits of bovine (b), ovine (o), and human (h) TSH was obtained by immunization with mixtures of purified bTSH and hTSH. RIAs showed that the antibody also bound the beta-subunits of bLH, oLH, hLH, and hCG, but not the beta-subunits of porcine LH and TSH. Preincubation of [125I]iodo-bTSH with the antibody completely inhibited binding of the hormone to the TSH receptor of bovine thyroid membrane preparations at pH 7.4 in 50 mM NaCl (ED50 = 10 nM). The antibody also inhibited TSH-induced mitogenesis of FRTL-5 cells (ED50 = 50 nM). We conclude that the antibody binds to a site on the bTSH molecule that participates in high affinity binding of hormone to physiological TSH receptor. The target epitope includes a conserved structural determinant in beta-subunits of the glycoprotein hormones as well as a feature that allows discrimination of porcine hormones from those of bovine, ovine, and human origin.
D000818:Animals; D000911:Antibodies, Monoclonal; D001667:Binding, Competitive; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D000939:Epitopes / Q000032:analysis; D006825:Hybridomas / Q000276:immunology; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D010446:Peptide Fragments / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D011863:Radioimmunoassay; D011989:Receptors, Thyrotropin / Q000378:metabolism; D013961:Thyroid Gland / Q000378:metabolism; D013972:Thyrotropin / Q000032:analysis* / Q000276:immunology / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000939:Epitopes; D010446:Peptide Fragments; D011989:Receptors, Thyrotropin; D013972:Thyrotropin