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Enzyme immunohistochemistry: review of technical aspects and diagnostic applications

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Abstract

The era of immunohistochemistry was introduced by Coons et al1 in 1941 when antibodies were successfully labeled with a fluorochromatic compound. Shortly thereafter, localization of tissue antigens was successfully accomplished with the use of fluorochromatic labels.2 Initially a research tool, immunofluorescence became an essential diagnostic technique for the evaluation of many disease states, particulary autoimmune diseases mediated by immune complexes or autoantibody deposition.

It soon became clear that certain limitations such as special instrumentation requirements and lack of permanency were accorded immunofluorescent procedures. Consequently, immunohistochemical systems were developed that permitted the visual localization of a tissue antigen as a permanent preparation with the potential for visualization of adjacent tissue morphology. The successful conjugation of antibodies with enzymes and unlabeled antibody methods made immunomicroscopy practical. Both enzyme-labeled antibody and unlabeled antibody (antienzyme) methods allowed identification of tissue antigens by formation of permanent color products in histologic sections with excellent morphologic detail.3,4

This paper reviews the rationale underlying enzymatic immunomicroscopic procedures, techniques currently available, characteristics of currently available chromogens, safety for personnel, quality control of immunohistochemical systems, and clinical diagnostic applications of the procedure.

Biochemistry of enzyme immunomicroscopy

Many different enzymes are potential antibody labels, including acid phosphatase, β-glucuronidase, 5′-nucleotidase, glucose oxidase, and horseradish peroxidase.5–7 However, horseradish peroxidase has been the enzyme label used most frequently since it is readily available and relatively inexpensive; well-established conjugation methods have been developed for conjugation with antibody.8

The biochemical reaction that occurs at the histochemical level can be summarized in the equation below: . . .


 

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