Immunohistochemistry Basics

Definition

Immunohistochemistry (IHC): Using the principle of antibodies binding specifically to antigens in biological tissues to detect the antigens (e.g.proteins) in cells of a tissue section.

Immunohistochemistry (IHC) is a process used to diagnose some types of cancer including mesothelioma. The procedure involves locating antigens in biopsy tissue through the use of a visual marker. Common markers include fluorescent dye, enzymes, colloidal gold and radioactive elements. If cellular events associated with cancerous tumors – such as an increase in cell death – are evident in the tissue, then the abnormal activity will be highlighted by the stained tissue sample. Immunohistochemistry cannot only help in the identification of a tumor, but it can also distinguish whether or not a tumor is benign or malignant.

History

The principle of IHC has existed since the 1930s, but it was not until 1941 that the first IHC study was reported. Coons and his coworkers used Fluorescein isothiocyanate (FITC)-labeled antibodies to localize Pneumococcal antigens in infected tissues. Since then, with improvement and development of protein conjugation, enzyme labels have been introduced, such as peroxidase and alkaline phosphatase.

Colloidal gold label has also been discovered and used to identify immunohistochemical reactions at both light and electron microscopy levels. Other labels include radioactive elements, and the immunoreaction can be visualized by autoradiography. All of these make immunohistochemistry a routine and essential tool in diagnostic and research laboratories.

Labels

There are a variety of fluorescent dyes and elements used to label the antibodies. These include peroxidase, colloidal gold, alkaline phosphatase and radioactive elements.

Use

The practice of immunohistochemistry is used to identify antigens in tissue samples in medical research. Doctors also use the method to diagnose diseases. It is a more accurate method than traditional enzyme staining diagnostic techniques.

Sample Heating

The scientist often uses different heating techniques, such as microwave heating or a pressure cooker, to reactivate the antigens in a tissue sample and make them more reactive to the dyed antibodies.