Immunoassay antibody-antigen reaction

Immunoassay is a method that identifies and quantifies unknown analytes usiag antibody—antigen reactions. Techniques are based ia immunochemistry, analytical chemistry, and biochemistry, with a history of development paralleling advances ia microbiology and immunology (see also Immunotherapeutic agents). 

Immunoaffinity chromatography (IAC), 6 400—402 12 137, 145 Immunoanalyzers, automated, 14 150 Immunoassay(s), 14 135-159. See also Immunoassay- DNA probe hybrid assays Immunoassay methods Immuno(bio)sensors antibody-antigen reaction, 14 136-138 basic technology in, 14 138-140 chemiluminescent, 14 150-151 classification of, 14 140-153 design of, 14 139-140 enzyme, 14 143-148 fluorescence, 14 148-150 highly specific, 14 153 historical perspective on, 14 136 microarrays and, 14 156—157 microfluidics in, 26 968—969 monoclonal versus polyclonal antibodies in, 14 152-153... 

Similar to the immunoassay techniques, radioimmunoassay, enzyme immunoassay, and chemiluminescence immunoassay are also applied and have proved useful. All techniques used for immunoassay represent coupling between the specificity of the antibody-antigen reaction and the sensitivity of the radiometric, electrometric, and chemiluminescence techniques. The limit of detection for immunoassay depends on the antibody affinity.128 130 Materials such as silica,131132 latex,133134 and alkylamine films135 are used for antibody absorption. SEM,136 scanning tunneling microscopy,137 and scanning force microscopy138 have been employed as tools for visualization of the immobilized antibodies. 

Sutherland R M, Dahne C, Place J F and Ringrose A S 1984 Optical detection of antibody-antigen reactions at a glass-liquid interface Clin. Chem. 30 1533-8 Jablonski E 1985 The preparation of bacterial luciferase conjugates for immunoassay and application to rubella antibody detection Anal. Biochem. 148 199-206... 

Immunosensor a Biosensor (see) which makes use of an antibody-antigen reaction to generate an electronic signal. Enzyme I. are based on competition between antigen and enzyme-linked antigen, so that sensor operation is equivalent to conventional enzyme immunoassay. See Field effect transistor. 

Immunoassays combine chemistry and immunology to test for specific analytes. Immunoassays detect antibody-antigen reaction. These tests are used in forensic science to analyse biological specimens for the presence of alcohol, drugs, toxins and poisons, and to determine causes of death in criminal investigations. 

An interesting recent review focuses on immunoassays that employ amperomet-ric array elements that have been coupled with magnetic separation principles [8]. Magnetic beads are suitably modified and used as a readily separated solid phase for antibody-antigen reactions, and electrodes modified with bioaffinity ligands provide array element-specific interactions and detection that, when individually addressed, allow the acquisition of unique signals for different analytes present in mixtures. 

EIAs can be used per se or with a spectrophotometer. Traditionally, EIAs have been developed in 96-weU microtiter plates which provide the immobilization support for the assay, the reaction vessel, and, when linked to a spectrophotometer-based reader, a rapid means to detect and quantify the color resulting from interaction of a substrate with the antibody—antigen—enzyme complex. Automated immunoassay analyzers targeted primarily for use in the clinical laboratory have taken automation one step further, utilizing robotics to carry out all reagent additions, washings, and final quantification including report preparation. 

A partially purified HIV viral lysate is laid onto a sodium dodecyl sulfate (SDS)-polyacrylamide gel slab and then electrophoresed, which distributes the HIV peptides through the gel by their relative molecular mass. The higher-molecular-mass proteins form bands near the top of the gel. The proteins on the gel are then transferred electrophoretically onto nitrocellulose paper. The paper is sliced into thin strips, each having the full distribution of HIV antigen bands. The strip is used as a solid support of an indirect immunoassay, and antigen-antibody reactions form insoluble colored bands on the strip. 

Other immunoassays are based on the same antibody-antigen binding reaction but use a different labeling system for detection. Instead of an enzyme label, there are radioactive isotopes, and fluorescent and luminescent labels. Some important immunoassays are defined below ... 

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