Monoclonal antibodies to human chorionic gonadotropin and their application to two-site sandwich radioimmunoassay.

Monoclonal antibodies were prepared against human chorionic gonadotropin (HCG). One monoclonal antibody recognized a conformational determinant expressed only on native HCG molecule and another monoclonal antibody had the specificity for the epitopes located on the beta-subunit of HCG. Monoclonal antibodies reacting with different antigenic determinants on the HCG molecule were used to develop a simplified 2-site sandwich radioimmunoassay in which one monoclonal antibody was immobilized and another labeled with 125iodine. This assay was highly specific for HCG and there was no cross-reactivity with alpha, beta-subunit of HCG, luteinizing hormone and follicle stimulating hormone.