Immunologic Studies of Purified Human and Bovine Thyrotropin

Abstract

The specificity of antisera to highly purified human and bovine thyrotropin (TSH) has been demonstrated by both in vitro and in vivo techniques. High titer rabbit anti-TSH sera were prepared to both antigens. Each of these antisera gave a single precipitin band with the homologous antigen and crude pituitary extract in agar gel diffusion studies. A TSH assay was developed employing radioimmunoprecipitation of purified TSH-I¹³¹ of high specific activity. This assay was capable of detecting as little as 0.01 mU of unlabeled homologous TSH. In both systems, no reaction was observed between either of the antisera to heterologous TSH, heterologous crude pituitary extract, or a variety of other pituitary hormones. Nonspecific inhibitors have prevented the assay of endogenous TSH in biological fluids. Biological neutralization studies were also performed using the newborn chick assay for TSH. The antisera in high dilution blocked the biological action of homologous TSH. Antisera to human TSH failed to neutralize bovine TSH even in doses greater than 25 times that required to completely neutralize human TSH. The bovine TSH antisera partially inhibited the biological action of human TSH when given in amounts 5-25 times that required to neutralize the bovine TSH.