Immunohistochemistry (IHC) is an important evaluation tool that falls under the umbrella of immunostaining techniques and exploits antigen–antibody binding to study the status of target molecules in tissues of interest. IHC, in combination with microscopy and image analysis techniques, has become a very powerful tool that offers a direct visualization of tissue antigens using labeled antibodies specific to the antigen. Owing to the versatility, simplicity and affordability of this technique, IHC is now indispensable to the fields of histology, pathology, cancer biology, neuroscience and drug discovery.
Antibodies are small protein molecules that are naturally expressed by the immune system of the body in response to the entry of a foreign molecule (antigen) and help in neutralizing it. Thus, antibodies act as a defense against potentially harmful foreign organisms and their products. The beauty of the antigen–antibody reaction is that each antibody is specific to only a portion of the antigen, called an epitope, and does not bind other molecules that do not match its target, including the body’s own molecules. All immunostaining techniques, including IHC, utilize this important property of the antigen–antibody reaction specificity to ensure the detection of a single molecule type from