immunoassay /im′yənō·as″ā/ [L, immunis + Fr, essayer, to try] , a commonly employed assay in which a solid-phase target antigen is designed to bind with an antibody in vitro to reveal its presence. When a conjugated antihuman immunoglobulin is added, it binds the antibody of interest. The conjugate, usually an enzyme, then reacts with its substrate to generate color or fluorescence that is proportional to antibody concentrations. See also enzyme-linked immunosorbent assay, radioimmunoassay, sandwich technique.
