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). 

The definition of an association constant for an antibody—antigen reaction can become more complex if the antibody—antigen reaction iavolves a multivalent antigen, as is the case when a polyclonal antisemm is used for detection of an antigen. This type of multivalent binding is termed avidity and is defined by the equation ... 

Definition of the association (or avidity) constant for such multivalent antibody—antigen reactions must consider not only the heterogeneity of the antibodies and the antigen determinant site(s), but also an apparent additive effect of binding two antigen molecules to a single antibody. Such effects lead... 

A novel fiber optic sensor concept using antibody-antigen reactions at a glass-liquid interface was reported by Daehne146. The reaction of antibodies immobilized onto the surface of fused silica fiber optic or planar waveguides with antigens in solution was detected by interaction with the evanescent wave. By detecting in-line fluorescence, the measurement of human IgG is described. 

Daehne C., Sutherland R.M., Place J.F., Ringrose A.S., Detection of antibody-antigen reactions at a glass-liquid interface a novel fiber-optic sensor concept, Proc. SPIE-Int. Soc.Opt. Eng. 1984 514 75. 

Y.-Q. Miao and J.-G. Guan, Probing of antibody-antigen reactions at electropolymerized polyaniline immunosensors using impedance spectroscopy. Anal. Lett. 37, 1053—1062 (2004). 

To recover quantitative concentrations from an assay, it is necessary to establish standard response curves for a particular antibody-antigen reaction. As an example,... 

Antibody-antigen complex, 14 149 Antibody-antigen reaction, 14 136-138 Antibody-based biosensors... 

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... 

Immunoradiometric assays (IRMAs) are like RIAs in that a radiolabeled substance is used in an antibody-antigen reaction, except that the radioactive label is attached to the antibody instead of the hormone. Furthermore, excess of antibody, rather than limited quantity, is present in the assay. All the unknown antigen becomes bound in an IRMA rather than just a portion, as in a RIA IRMAs are more sensitive. In the one-site assay, the excess antibody that is not bound to the sample is removed by addition of a precipitating binder. In a two-site assay, a molecule with at least two antibody-binding sites is adsorbed onto a solid phase, to which one of the antibodies is attached. After binding to this antibody is completed, a second antibody labeled with 125I is added to the assay. This antibody reacts with the second antibody-binding site to form a sandwich, composed of antibody-hormone-labeled antibody. The amount of hormone present is proportional to the amount of radioactivity measured in the assay. 

V. Hlady, J. N. Lin, and J. D. Andrade, Spatially resolved detection of antibody-antigen reaction on solid/liquid interlace using total internal reflection excited antigen fluorescence and charge-coupled device detection, Biosens. Bioelectron. 5,291-301 (1990). 

C. Dahne, R. M. Sutherland, J. F. Place, and A. S. Ringrose, Detection of anti body-antigen reactions at a glass-liquid interface A novel fibre-optic sensor concept, Corf. Proc. OFS 84, 2nd International Conference on Optical Fiber Sensors, pp. 75-79 (1984). 

As noted above, the specificity of the antibody-antigen reaction is critical for obtaining reliable, interpretable results. For this reason, the antibody has to be tested rigorously, and essential controls for antibody specificity should be included in any experimental design. A comprehensive discussion on antibody generation, specificity, and testing for immunocytochemical applications can be found in references (27-29) and, for specific applications, see Chapters 17, 50, and 51. 

Inhibition of enzyme activity was not used to assess the antibody-antigen reaction of lignin-peroxidase, as the addition of control serum to enzyme reaction mixtures increased the pH above the pH specificity of the... 

Giaever, I., 1973. The antibody-antigen reaction a visual observation,/. Immunol., 110, 1424-1426. 

Once antibodies and antigens have been developed, they must be incorporated into an assay system for visualization of the primary antibody-antigen reaction. To accomplish this task effectively, an assay format and procedures to visualize the antibody-antigen reaction must be first selected, the necessary reagents must then be prepared, and the final immunochemical method including sample preparation must be optimized for the intended application. 

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