immunohistochemistry
Meaning of immunohistochemistry: A staining method that uses antibodies to make one chosen protein visible in a slice of tissue, while everything else stays pale.
Definition of immunohistochemistry
Immunohistochemistry is a laboratory method that locates a specific protein inside a slice of tissue by using an antibody that sticks only to that protein. A colored or fluorescent label attached to the antibody makes the binding site visible under a microscope. Because the tissue structure is preserved, the result shows not just whether the protein is present but exactly which cells contain it.
How does the staining work?
A thin slice of tissue is fixed to a glass slide. An antibody raised against the target protein is washed over it and binds wherever that protein sits. Unbound antibody is rinsed away. A second step attaches a label, usually an enzyme that turns a colorless chemical brown at the binding site. Under the microscope the target appears as brown staining against a pale blue counterstain, and its position within the cell can be read directly.
What does it tell a pathologist?
Two things above all: what a cell is, and how it is behaving. Many tumors look similar under ordinary staining, and the pattern of proteins they carry gives away their origin.
| Question | What the stain shows |
|---|---|
| Where did this tumor start? | Proteins typical of a tissue of origin |
| Will hormone treatment work? | Presence of hormone receptors |
| Is a target drug an option? | Overexpression of a target protein |
| Is an infection present? | Proteins from the organism itself |
Where can it mislead?
The method is sensitive to handling. Tissue left too long before fixing, or fixed for the wrong length of time, can lose the very protein being hunted, producing a false negative. Antibodies also cross-react, binding weakly to proteins that resemble the intended target, so a stain read in isolation can point the wrong way. For this reason results are interpreted as a panel rather than one at a time, with positive and negative control slides run alongside. No single marker is unique to one tissue, so a diagnosis of cancer and of its origin rests on the pattern across several stains together with the appearance of the cells themselves.
Also known as
Used in a sentence
Immunohistochemistry was positive for cytokeratin and negative for lymphoid markers.
Good to know
Results depend heavily on how the tissue was fixed and processed, and stains are interpreted as a panel with controls rather than as single positive or negative answers.
Word origin
Where “immunohistochemistry” comes from
Combines immuno-, from the Latin immunis meaning exempt, with the Greek histos, meaning tissue, plus chemistry.