Immunohistochemistry (IHC) staining: It uses antibodies to detect the location of proteins and other antigens in tissue sections. The antibody-antigen interaction is visualized using either chromogenic detection with a colored enzyme substrate, or fluorescent detection with a fluorescent dye. The tissue sides used for IHC staining are the same as that for H&E described above, the difference being that instead of H&E stain, special antibody (i.e. marker proteins) are used. The marker proteins characteristic of particular cellular events such as proliferation or cell death (apoptosis) or certain cancer sub-types are selected.
Usually, IHC stating is performed using chromogenic detection approach. Here, in the region where the target protein is present (i.e. antibody-antigen interaction) is colored dark-brown and rest of the region are colored light blue. Furthermore, pathologist often quantify the abundance of protein in the tissue slide be scoring (or estimating) the total stained area (i.e. dark-brown colored area) within the tumor tissue present in the slide.