Immunohistochemistry (IHC) uses antibodies to detect antigens in a tissue sample. It’s one lab technique a pathologist may use to check for signs of disease following a biopsy. IHC is commonly used to diagnose cancer, predict treatment response and determine likely outcomes (prognosis) of the disease.
Immunohistochemistry (IHC) is a lab technique pathologists use to look for signs of disease in a tissue sample. A pathologist uses lab tests to diagnose medical conditions.
As part of your diagnosis, a healthcare provider may remove tissue and send it to a lab for testing. For example, they may remove part of a tumor and send it to a lab to test for cancer cells. This is called a biopsy. An IHC is just one method a pathologist may use to study the sample once it arrives at the lab.
IHC is the most common type of immunostaining. Immunostaining involves using antibodies and special markers to “label” parts of a tissue sample so they’re easier for pathologists to identify.
The word “immunohistochemistry” provides clues about what’s involved:
An IHC can be used to:
Researchers also perform IHC to develop new drug treatments. IHC helps researchers learn more about how the smallest parts of your body work, like your cells and the molecules inside them. IHC provides insight into how diseases affect these processes and what treatments can help.
It can identify pathogens that cause infection, too. The first successful IHC stain occurred in 1941, when researchers (Coons, et al.) identified the bacteria associated with pneumonia (pneumococcus) in a tissue sample.
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An IHC uses antibodies to detect a target antigen in a tissue sample. The target antigen is a marker, indicating a specific disease is present. If the antibody recognizes the antigen, it will attach (bind) to it. The binding process is similar to a lock (antigen) and key (antibody). If the antibody binds to the antigen, the tissue sample will stain a certain color when viewed beneath a microscope.
It works like this:
For the results to be reliable, pathologists must accurately complete multiple steps.
Preparing the sample ensures it stains correctly. If an antigen is present, it stands out in colored segments against the background. To prepare the sample, pathologists:
Pathologists select antibodies known to bind to the target antigen. IHC uses either polyclonal antibodies or monoclonal antibodies.
Pathologists prepare the antibody to stain tissue containing the antigen.
The first successful IHC used a similar process. Instead of linking the antibody to an enzyme, the researchers linked it to a fluorophore. A fluorophore absorbs light and reflects it. The fluorophore stains the sample when viewed under a fluorescence microscope. This technique is now considered a different type of immunostaining called immunofluorescence.
There aren’t standard guidelines for each step in immunohistochemistry. Different labs use different techniques, which means results may vary.
Also, recent research has shown that not all antibodies available for IHC do what they’re supposed to — that is, detect the target antigen in a sample. If there are problems with the antibodies, a test may give results that are false, including:
Labs must have quality controls in place so that every step preserves the tissue and ensures a high-quality stain. To improve IHC accuracy, pathologists can test antibodies on tissue known to contain the target antigen to ensure it stains before testing an unknown tissue sample.
When performed correctly and with quality controls in place, immunohistochemistry is a reliable method for cancer diagnosis. One study reports that IHC can accurately identify the primary location of metastatic cancer with 70% to 90% accuracy.
No, but they’re related. Immunohistochemistry is one type of lab technique a pathologist may perform on a tissue sample collected for a biopsy.
A note from Cleveland Clinic
Immunohistochemistry (IHC) allows pathologists to achieve something remarkable. It enables them to see signs of disease invisible to the naked eye. IHC uses your body’s powerful fighters, antibodies, to expose harmful, microscopic substances that cause disease. It’s just one method that allows scientists to study, diagnose and — most importantly — fight cancer from the lab.
Last reviewed by a Cleveland Clinic medical professional on 06/20/2023.
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