A clinical-shaped marker is read as present or absent, retained or lost, mutant or wild type, and that binary is what makes the reagent's specificity a serious matter rather than a preference. Every antibody in this class needs a documented pattern, an internal control in the same section, and evidence against the thing it must not detect.
What a mutation-specific clone has to prove
An antibody claiming to detect a single amino acid substitution has to be shown not to bind the wild type protein or the other substitutions at the same position, on material of known genotype, at the sensitivity a section demands. That evidence is a panel of cell lines or tissues with sequencing behind them, not a peptide competition. Where it does not exist, sequencing remains the method and the antibody is a screening tool at best, which is how most laboratories should treat this class.
A brca1 antibody and an mgmt antibody on repair status
Both are read as loss, and loss is the hardest thing to prove with an antibody: weak retrieval, a thin section or an aged block all read as absent. So an internal positive control within the same section, a known positive on the same run and a documented protocol are what make the call defensible. For the methylation-silenced repair enzyme, the molecular assay on the promoter is the reference method and the stain is an adjunct rather than a replacement.
An hdac3 antibody and a p62 antibody on epigenetic and aggregate markers
The deacetylase is one of a family sharing domains, so the immunogen decides whether the member or the class is reported, and it sits in complexes, which makes immunoprecipitation the informative experiment and a gentle lysis part of it. The autophagy adaptor accumulates as inclusions when degradation fails, so its readout is puncta or inclusion bodies in tissue rather than a band, and a flux design is needed before any statement about autophagy.
An hla-g antibody and a cd71 antibody on immune privilege and iron
The non-classical major histocompatibility molecule is expressed in placenta and in some tumours, and its clones have a reputation for cross reacting with classical molecules, so the specificity evidence has to name what was excluded. The transferrin receptor is a proliferation and iron uptake marker whose expression rises with demand, which makes it a poor lineage marker and a useful state one, read on the surface by flow cytometry.
An il23r antibody and a ddr2 antibody on receptors read in tissue
Both are membrane receptors at low abundance with the difficulties that class brings: a glycosylated band, buried epitopes and clones that stain knockout material in published comparisons. For the cytokine receptor the population it marks is defined in combination with other markers, and for the collagen receptor the informative readouts are phosphorylation after ligand and a genetic control. Neither supports a conclusion on one clone alone.
Retained or lost, and the controls that binary needs
When a result is binary, the controls are not optional: a known positive tissue, a known negative, a no-primary section, and best of all an internal control within the section that experienced the same fixation and retrieval. A weak stain then means what it should, and a laboratory can defend a call. Without them, loss is indistinguishable from an old block, a long fixation or a tired detection kit, which is the commonest source of an error that reaches a report.
Where the molecular assay is the reference
For mutation status, promoter methylation, copy number and fusion detection, a molecular method is the reference and the antibody is a triage: cheaper, faster, available on a section, and less specific. Saying which role the stain plays in the workflow, and what happens when the two disagree, belongs in the method rather than in a footnote. An antibody result contradicting a sequencing result is usually the antibody, and the workflow should say so in advance.
What to ask for on this class
Ask for the genotyped or characterised material the clone was validated on, the expected pattern and its internal control, the retrieval conditions, and whether a diagnostic grade version exists if the result will support a clinical decision. Ask what the clone does not detect, since for a mutation-specific or loss-of-expression marker the negative claim is the product. Record the clone, the lot and the protocol with every reported case.
Questions people ask about kras g12d antibody
Can a mutation-specific antibody replace sequencing?
Rarely. It has to be shown not to bind the wild type or other substitutions on genotyped material, and even then it is usually a triage tool.
Why is loss harder to prove than presence?
Because weak retrieval, an aged block or a tired detection system all read as absent. An internal positive control in the same section is what separates them.
What happens when a stain and a molecular result disagree?
The molecular method is the reference for mutation, methylation, copy number and fusions, and the workflow should state that in advance.