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Clinical Chemistry

  1. Christopher P. Price

Published Online: 15 SEP 2006

DOI: 10.1002/9780470027318.a0526

Encyclopedia of Analytical Chemistry

Encyclopedia of Analytical Chemistry

How to Cite

Price, C. P. 2006. Immunochemistry. Encyclopedia of Analytical Chemistry. .

Author Information

  1. St. Bartholomew's and the Royal London School of Medicine and Dentistry, London, UK

Publication History

  1. Published Online: 15 SEP 2006


Immunochemistry is a generic term to describe all analytical methods that employ the reaction between an antigen and its complementary antibody for the recognition and/or quantitation of an analyte. The analyte may be the antigen or antibody and in each case the complementary species (antibody or antigen, respectively) will be the primary reagent in the analytical system. The analyte may be present in free solution (e.g. in blood, urine, fermentation broth, effluent, etc.) or may be structurally incorporated in a cell (e.g. red cell, bacterium, virus particle) or solid tissue. Our knowledge of the chemical structure and reactivity of the combining sites of antigens and antibodies (epitopes and paratopes, respectively) has meant that antigen- and antibody-like species can now be synthesized. In the former case this may be undertaken to provide an appropriate immunogen or calibration material whilst several antibody mimics have been demonstrated.

The immunoassay format will depend on the purpose for which the assay is to be used. In that the antigen–antibody reaction is unique to two complementary partners, in terms of cells and tissues, there is no other technique that will provide the same specificity – with the exception of DNA. Quantitative assays are usually required for the analysis of molecules in complex fluids. In the research phase, chromatographic techniques, e.g. high-performance liquid chromatography (HPLC), gas chromatography (GC), or capillary zone electrophoresis (CZE) can provide the characterization and quantitation required; however, these techniques are not always applicable when the need for the assay is established and a large workload is envisaged. An immunoassay then provides the necessary specificity and workload capability. In addition, when assays are used outside the laboratory, e.g. at the bedside, then only immunoassays are applicable because they can be encapsulated in microfabricated devices.

This article describes the underlying principles of immunoassay, the design of reagents and assay formats, and illustrates their application to a wide range of analytes.