Abstract: The present invention relates to compositions comprising novel reduced cortisol conjugates, methods for their preparation and use in immunoassays for cortisol. In another aspect, it relates to conjugates of reduced cortisol as immunogens or haptens for eliciting anti-cortisol or anti-reduced cortisol antibodies.

Abstract: Specific binding ligands can be detected with an assay which utilizes an immobilized receptor for the ligand, an immobilized reporter enzyme, an inhibitor antibody and a a water-soluble conjugate of the ligand and an anti-inhibitor antibody. Both antibodies are specific for the reporter enzyme, but the antibodies affect enzymatic activity differently. The inhibitor antibody effectively shuts down the activity of the reporter enzyme when it is complexed thereto. The anti-inhibitor antibody binds to the reporter enzyme, does not affect the enzymatic activity, but prevents the binding of the inhibitor enzyme. This assay provides a direct correlation of the generated signal to the target specific binding ligand.