Immunoperoxidase techniques in Dermatopathology

This report is a review of the immunoenzymatic methods commonly used in dermatology. The values and limitations of the techniques and problems encountered in carrying out the procedures are discussed. Examples of the range of antigens detectable by these methods are given and the type of technique available for different antigen locations is illustrated. Immunopathology developed following the successful demonstration by Coons in 1942 of pneumococcal antigen in tissue using fluorescein conjugated antibodies. Although easy to perform, Coons' technique had several limitations. The special microscopy required to visualize the fluorescein precluded correlation of the image with the conventional histological features, Furthermore the specimens could not be stored and they could not be processed for ultrastructural examination. Singer attempted to solve this latter problem in 1959 by using electron dense ferritin labelled antibodies, but these were invisible in light microscopy. Thus, the development of enzyme labelled antibodies (Avrameas & Uriel, 1966; Nakane & Pierce, 1966) which allowed visualization of antigens in both light and electron microscopy represented a considerable technological advance and these methods became rapidly established in general pathology. The permanence of the sections which could be counterstained and viewed with a conventional microscope also enhanced the popularity of these techniques. Many enzymes were used in conjugation with antibodies including glucose oxidase, alkaline phosphatase (Avrameas, 1969) and acid phosphatase (Nakane & Pierce, 1967) but the simplicity and technical superiority of horseradish peroxidase (HRP) and its commonly employed substrate 3,3′-diaminobenzidine ensured that this combination became the most widely used.