Allowance for antibody bivalence in the characterization of interactions by ELISA

The objective of this review is to remove empiricism from the characterization of immunospecific interactions by enzyme-linked immunosorbent assay (ELISA). In place of the original presumption that the absorbance generated by the enzyme-linked assay could be regarded as a measure of free antibody concentration, the stance is taken that the parameter being monitored is the concentration of antibody complexed with immobilized antigen on the microtiter plate. After the presentation of general binding theory that takes ligand multivalence into account, that theory is adapted to incorporate the simplifying circumstances that prevail in an ELISA study. Validity of the original expressions for characterizing antigen-antibody interactions by competitive ELISA is confirmed, thereby refuting reported concerns about the need for amendment of the theoretical expressions to take into account bivalence of the antibody.