In the previous units of this series, the immunohistochemical (IHC) methods of immunofluorescence and immunoperoxidase were described and discussed. These methods use antibodies to localize cellular proteins in tissue sections, which can then be visualized in either a dark field fluorescence microscope or routine bright field microscope. It is important to understand antibody structure and function in order to fully appreciate these immunohistochemical (IHC) techniques.
In the previous segment, immunofluorescence methods were discussed. These methods use antibodies labelled with fluorescein to directly localize cellular proteins in tissue sections, which can then be visualized in a dark field fluorescence microscope. Despite the advantages of this method, science is always in search of newer methods to gain more knowledge. Thus in 1970 Sternberger et al (1970) reported an improvement of Graham’s method (1965) using horse radish peroxidase enzyme (HRP) labelled antibodies to localize antigens and visualize them in the routine light microscope – bringing the method “to light” as one might describe. Now researchers and pathologists could see protein localization within the histology of formalin fixed paraffin embedded tissues viewed using a routine bright field microscope. This provided vast improvements over the immunofluorescence method.
Anthony van Leeuwenhoek is credited with being the first person to use a microscope to view tiny “animacules” in 1674. At approximately the same time, Robert Hooke used a similar microscope to view thin slices of cork. The structures that he observed resembled the tiny cells that monks lived in at the local monastery, so he named the structures “cells”.