Development and characterization of a monoclonal antibody which distinguishes the beta-subunit of human chorionic gonadotropin (beta hCG) in the presence of the hCG.

A monoclonal antibody specific for the β-subunit of human chorionic gonadotropin (βhCG) has been developed which has a cross reactivity of 0.23% with intact hCG. There was no cross reactivity with other glycoprotein pituitary hormones in the range in which they might be expected to be present in serum. The Β-subunits of hFSH, hTSH and hLH did not inhibit binding of [125I]iodo-βhCG to the antibody at up to 250 ng/tube. The dissociation constant (Kd) with [125I]iodo-βhCG was 3.3 × 10-10, and the reaction had reached equilibrium within 1 h.