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Knowledge articleImmunohistochemistry (IHC): What It Is and How It Works
Using antibodies to show exactly which proteins a tissue is expressing.
H&E tells you what tissue looks like. Immunohistochemistry — IHC — tells you what it's actually made of. By using antibodies that bind one specific protein, IHC lights up exactly where that protein sits in a tissue section, which is how modern pathology subtypes tumours, finds their origin, and guides treatment.
The core idea
An antibody is raised against a target protein (an antigen). Apply it to a tissue section and it binds only where that protein is present. A detection system then makes that binding visible — usually as a brown deposit — under the microscope. Brown where the protein is; counterstain everywhere else.
How an IHC run goes
- Section and dewax FFPE tissue onto charged slides.
- Antigen retrieval — heat or enzyme treatment to un-mask epitopes that fixation hid.
- Block background binding.
- Primary antibody — binds the target protein.
- Detection — a labelled secondary system plus a chromogen (commonly DAB) produces the visible signal.
- Counterstain (usually haematoxylin), dehydrate and mount.
Why controls make or break it
IHC is only trustworthy with the right controls on every run — a known positive (tissue or cells that should stain) and a negative. Without them, a failed stain can masquerade as a genuine negative result. This is where defined, reproducible controls matter — see cell line microarrays as IHC controls and IHC controls and reproducibility.
Consistency, again
Like H&E, IHC lives or dies on reproducibility — of retrieval, incubation times and reagent handling. Standardising those steps (manually disciplined, or on an automated platform/stainer) is what keeps results comparable from day to day and slide to slide.
FAQs
What is immunohistochemistry (IHC)?
A technique that uses antibodies to detect and localise specific proteins in a tissue section. Where the antibody binds its target protein, a detection system produces a visible (usually brown) signal under the microscope.
What is the difference between H&E and IHC?
H&E shows general tissue architecture by staining nuclei and cytoplasm. IHC shows the presence and location of a specific protein using antibodies, which helps subtype tumours and guide treatment.
Why are controls important in IHC?
A known positive and negative control on every run confirm the stain worked. Without them, a failed run can look like a true negative result and be misread.
Prepared and reviewed by the Unimeditrek technical team based on laboratory practice, installation and service experience. This document explains histopathology workflow, laboratory practice and equipment based on the questions we hear from hospitals, medical colleges and diagnostic laboratories — vendor-neutral where it explains the science and practical where it explains equipment.
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