Two-site sandwich enzyme immunoassay with monoclonal antibodies to human alpha-fetoprotein.

Monoclonal antibodies reacting with different antigenic determinants on the alpha-fetoprotein (AFP) molecule were used to develop a simplified 'sandwich' ELISA (enzyme-linked immunospecific assay) in which one monoclonal antibody was immobilized and another labeled with an enzyme. Due to their different specificities the antibody attached to the solid phase and the one conjugated to the enzyme did not compete for binding to AFP making it possible to complete the two antigen-antibody reactions required in a single, short incubation. The rapidity, simplicity and excellent sensitivity of this assay combined with the exquisite specificity associated with the use of two monoclonal antibodies make us believe that assays based on this principle will be useful in the quantitation of substances of medical and biological importance.