Qualification for Staining Immunohistochemistry

Immunohistochemistry (IHC) has been a powerful tool for diagnosing cancer and other diseases. Breast tumors are routinely evaluated by IHC for the presence of specific biomarkers -- proteins -- such as estrogen receptors, and therapies designed according to the results.

Tissues

• Tumor biopsy samples can be frozen or embedded in paraffin, sliced into thin sections and placed on slides. Blood cells or cell lines growing in a laboratory can also be placed on slides for examination. The samples are fixed to the slides with methanol or formaldehyde.

Antibodies

• Antibodies are part of the body's defense against foreign proteins present on a bacteria or virus for instance. An antibody is specific for a single protein; this protein target is known as an antigen. For breast cancer IHC, antibodies have been developed commercially that are specific for the estrogen receptor protein. Fixed breast biopsy sections are incubated in a solution containing the estrogen receptor antibody, and if the receptor is present, the antibody will bind to it.

Visualization

• To see the antibodies, they are linked to markers that can dye the tissue, such as horseradish peroxidase (HRP), or to fluorescent markers such as green fluorescent protein. The slides can be viewed under the appropriate microscope, and the estrogen receptors will be marked in the tissue if they are present.