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Characterization of a Bioeffective Monoclonal Antibody against Thyrotropin β-Subunit^*

Department of Microbiology, Cancer Center (B.L.H., B.F.E.) and the Department of Medicine, Columbia University (J. W.L.) New York, New York 10032

Address requests for reprints to: Dr. Bernard F. Erlanger, Department of Microbiology, Columbia University, 701 West 168th Street, New York, New York 10032.

Abstract

To describe a region of the TSH molecule participating in binding to receptor, a monoclonal antibody specific for a TSH epitope shared by β-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 β-subunits of bLH, oLH, hLH, and hCG, but not the β-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 β- subunits of the glycoprotein hormones as well as a feature that allows discrimination of porcine hormones from those of bovine, ovine, and human origin. (Endocrinology 120: 574–581, 1987)

Footnotes

^* This work was supported by a NSF predoctoral fellowship (to B.L.H.), NIH Grant NS-15581, NICHHD Grant HD-15454-05, and a grant from the Muscular Dystrophy Association. This paper is in partial fulfillment of the requirements for the Ph.D. degree in the Department of Microbiology, Columbia University.

Received June 6, 1986.