ANTIGONADOTROPHIC PROFILE OF ANTISERA AGAINST HUMAN GONADOTROPHIN PREPARATIONS

ABSTRACT Forty-two antisera were prepared in rabbits against human chorionic gonadotrophin (HCG), human hypophysial gonadotrophin (HHG), human urinary luteinizing hormone (LH) and human menopausal gonadotrophin (HMG) preparations. The gonadotrophic profiles of the antigens were previously characterized by bioassay, immunoassay and bioimmunoassay methods. The 25 most potent antisera were tested in statistically valid bioassays for their HCG and follicle stimulating hormone (FSH) neutralizing activities as well as for their neutralizing potencies against the FSH-like activity present in HCG preparations. The anti-HCG/anti-FSH ratios of the anti-HCG sera tested varied between 6.2 and > 254, while those of the anti-HHG, anti-LH and anti-HMG sera were close to 2. It was found that the total dose of immunological activity (anti-HCG neutralizing and anti-FSH neutralizing potency) rather than that of the biological activity administered to the rabbits was decisive for obtaining antisera with high anti-HCG and anti-FSH titers. Immunization with a highly purified HCG preparation (> 17 000 IU/mg) resulted in antisera exhibiting lower anti-HCG/anti-FSH ratios than did immunization with partially purified preparations. A highly purified urinary LH preparation which did not contain any detectable FSH activity gave rise to antisera exhibiting anti-HCG/anti-FSH ratios of approximately 2.0. These highly purified HCG and LH preparations were shown previously to possess high anti-FSH neutralizing potencies (Petrusz et al. 1971b). Booster injections did not change significantly the quality or the titer of the antigonadotrophic sera studied. The HCG neutralizing potency of anti-HCG sera was approximately 3 times higher when assayed against a highly purified HCG preparation (> 17 000 IU/mg) as compared to potency estimates obtained against the laboratory standard of HCG (about 2000 IU/mg). It is suggested that consideration should be given to the establishment of standard preparations of antigonadotrophic sera. It is concluded that bioimmunoassays are more suitably than conventional bioassay methods for the assessment of the antigenic purity of human gonadotrophin preparations.