JavaScript is disabled in your browser. Please enable JavaScript to view this website.

Best practice for validating antibodies for IHC

This guide outlines practical, evidence‑based steps to validate antibodies for IHC, drawing on community‑endorsed recommendations and widely used validation frameworks.

High‑quality immunohistochemistry (IHC) starts with choosing an antibody you can trust. A well‑validated antibody allows you to confidently interpret tissue localization, compare expression across samples, and build reproducible data that withstands scrutiny. At the heart of any successful IHC experiment is a reagent that is specific, sensitive, and consistent; three qualities that determine whether the staining you see reflects true biology or technical artefact.

Specificity ensures the antibody recognises the intended target with minimal cross-reactivity; sensitivity determines how well low‑abundance or dynamic expression is detected; and reproducibility underpins every comparison you make across tissues, experiments, or colleagues.

1. Understand your target

Understanding your protein of interest is the first and most important step in IHC validation. The clearer your expectations, the easier it is to determine whether an antibody is performing correctly. It’s vital to understand the expression profile, biological function and genetics of the target. This information will help you identify relevant controls, build an antibody shortlist, and decide how to interpret your data.

Expression profile: where and how the protein is expressed

Before ordering or testing an antibody, gather information about:

Looking at published IHC data for your target is a good starting point. Literature reviews and antibody vendors’ websites are a useful place to find data, as are resources like the Human Protein Atlas (HPA), which provide detailed IHC‑based expression maps across human tissues.

Biological function: does the staining make sense?

Protein function often predicts localisation. Transcription factors are nuclear; membrane receptors show crisp membranous staining; mitochondrial proteins localise to discrete granular cytoplasmic compartments. Understanding function helps you recognise plausible staining versus questionable patterns.

Genetics, isoforms and post-transcriptional modifications

Some targets are more challenging due to:

Databases like Ensembl, UniProt, GeneCards, and OMIM provide insights into isoforms, sequence similarity, variant biology, and clinically relevant features. This information helps you anticipate potential cross‑reactivity risks and select antibodies that target unique, stable epitopes.

2. Select high‑quality control materials

Your choice of control material directly influences how convincingly you can demonstrate antibody performance. Robust validation always includes both positive and negative controls.

Positive controls: demonstrate true target detection

Positive controls should be tissues or cells that express the target at levels appropriate for your biological question. Ideally, they cover:

Tissue microarrays (TMAs) enable efficient, standardised examination of multiple tissues under identical staining conditions, supporting higher‑confidence interpretation and improved reproducibility. [proteinatlas.org], [data.atlas...bodies.com]

Negative controls: reveal background and non‑specific binding

Negative controls detect unwanted signal from sources such as endogenous peroxidase, Fc receptor engagement, or off‑target antibody binding. Strong negative controls include:

Control material examples

Endogenous expressing material

Cultured cells: can be used to make FFPE cell blocks

Tissue: using tissue is essential because it gives insight into non- specific antibody binding. Protein expression levels are often modulated in disease and so it can be useful to use disease tissue combined with matched normal tissue. Tissue microarrays (TMA) can maximise data generated with uniform technical parameters (all samples are on the same slide so are exposed to the same experimental conditions).

Pre-analytical factors, like fixation, variation, and block storage, can have a big impact on IHC results. It’s good practice to validate your control tissue quality before using it to validate your antibody. This can be done by performing IHC on the samples using a trustworthy antibody targeting a well understood protein.

Material with manipulated/modulated expression levels

Genetically modified cells: KO cell lines can be generated using CRISPR-Cas9 technology to knock out the target of interest, creating a negative control. You can use KO cell lines and matched WT control cells to make FFPE cell blocks. Validating antibodies using this approach, whether with cell-based or animal knockout models, is widely regarded as a gold standard for assessing antibody specificity.

RNA knock down: if KO cell lines aren’t available, siRNA can be used to knock down target gene expression.

Over-expressing cell lines: plasmid transfection can be used to create cell lines overexpressing the target protein or closely related family members. This allows for assessment of cross-reactivity.

When using modulated material, it’s worth asking if your KO is a true KO or if truncated protein remains in your sample. Tagging your target protein with Myc or His can be used as a positive control for transfection.

Build confidence in your control material by using orthoganal techniques for target detection, eg western blot and flow cytometry on cell lysates, or ISH for RNA detection in tissue.

3. Optimise your IHC assay parameters

Once your target biology and controls are in place, the next step is to optimise the staining protocol to reveal the antibody’s true performance. Your antibody vendor’s datasheet, as well as peer-reviewed publications using the antibody, can provide guidance as to IHC conditions which you can use as a starting point before developing the assay in your lab. The two key experimental parameters you need to test are epitope retrieval and antibody concentration.

Epitope retrieval

Formalin cross‑linking often hides epitopes, making retrieval essential. Testing both acidic (pH ~6 with NaCl) and alkaline (pH ~9 with EDTA) heat‑induced epitope retrieval (HIER) conditions helps identify which buffer best exposes your target.

Antibody titration: finding the optimal balance

Titrating your antibody across a dilution range ensures you identify the concentration that delivers:

This step is essential: even a highly specific antibody can appear “non‑specific” at too high a concentration or “insensitive” at too low a concentration.

Essential internal assay controls

To understand background signal and non‑specific interactions:

Detection systems and automation

Commercial detection kits provide standardised sensitivity and reproducibility, reducing lab‑to‑lab variability. Consider using automated staining platforms as they offer reproducibility, sensitivity, reduction in operator error rate and tracking capabilities.

Independent antibodies: strengthening evidence of specificity

Testing a second antibody raised against a different epitope on the same target provides powerful corroboration. When staining patterns agree, particularly in combination with KO material, you significantly increase confidence in specificity.

Quick validation checklist

Use this checklist to ensure your IHC antibody is fully validated:

References

noTranslate
GlobalLinkNoTx

Learn more about our commitment to testing the quality of our antibodies

Learn about our collaboration with YCharOs
button-primary