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 beta-subunit of human chorionic gonadotropin (beta hCG) has been developed which has a cross reactivity of 0.23% with intact hCT. 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 beta-subunits of hFSH, hTSH and hLH did not inhibit binding of [125I]iodo-beta hCG to the antibody at up to 250 ng/tube. The dissociation constant (Kd) with [125I]iodo-beta hCG was 3.3 x 10(-10), and the reaction had reached equilibrium within 1 h.