Highly Specific and Sensitive Hybridoma Antibodies against the α-Subunit of Human Glycoprotein Hormones*

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Abstract
The free .alpha.-subunit of human CG (hCG-.alpha.) has been detected in pregnancy as well as in several endocrine and nonendocrine tumors. In order to facilitate the detection of these tumors, we have developed, by hybridoma technology, very sensitive and highly specific antibodies of hCG-.alpha., A2D4 and A2-58. Employing these antibodies, assays were developed to detect picogram levels of the free .alpha.-subunit. These antibodies have negligible cross-reactivity with intact hCG (A2D4, 0.17%; and A2-58, 1.75%). Pituitary hormone standards of human LH, human FSH, and human TSH from NIH showed cross-reactivity with these antibodies. However, the cross-reactivity was found to be due to the contamination of the hormone preparations with .alpha.-subunit. The antibodies have no effect on the binding of hCG to its receptor. They cross-react to the same extent with the deglycosylated hCG-.alpha. and .alpha.-subunits of all other human glycoprotein hormones but do not react with .alpha.-subunits of glycoprotein hormones from other species. We have purified these antibodies to homogeneity by DEAE Affi-Gel Blue and affinity chromatography. Both these antibodies belong to immunoglobulin M subclass.
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