Custom antibody projects: when custom antibodies beat a catalogue reagent or an antibody catalog listing, where research antibodies and antibodies for research bought off the shelf are the faster answer, what gmp antibodies require that a research grade does not, and the specification that decides whether yours works

Deciding and specifying

1. Rule the catalogue out properly first. Before commissioning, establish whether existing reagents genuinely fail or were used outside their validated application. A catalogue antibody validated for one application and used in another is the most common false negative, and finding that out costs a great deal less than a custom project.
2. Write the application into the specification. State the assay, the sample type, the fixation and the species. An antibody that must work on fixed tissue, on a denatured blot and in a live-cell assay is three different reagents, and a provider that agrees to all three without comment is not reading the request.
3. Choose the epitope deliberately. Where you raise against determines what you can distinguish: an isoform, a modification state, a species orthologue or a domain. Say what must be discriminated and what must be recognised across, and require a counter-screen that tests it.
4. Plan validation before the project starts. Decide what evidence will convince you the antibody works, including a genuine negative control such as a knockout or knockdown sample. Projects without a defined acceptance test end in an argument about whether a band is the right band.
5. Secure renewability. Ask for the sequence or the clone. A custom polyclonal is a finite reagent, and a programme that will run for years should pay the extra for something that can be made again.

Where custom projects actually fail

The common failures are an immunogen that does not represent the folded protein, a screen that does not resemble the application, and the absence of a real negative control during validation. All three are decided before any animal is immunised, which is why the specification conversation is the project.

A less common but expensive failure is a target so conserved that the host does not raise a response. Providers can often predict this from the sequence, so ask before contracting.

What you should receive

The antibody in a stated format and buffer, the immunogen description, the screening data including the counter-screen, the validation data in the specified application, a lot certificate, and the clone or sequence where the contract provides for it.

Ask for a retained reference aliquot. It is the only way to test a future lot against the reagent you originally validated.

Common questions

When should I order a custom antibody?

When no catalogue reagent exists for the target, when you need to distinguish an isoform, modification or species that existing reagents cannot, or when you have genuinely established that available reagents fail in your validated application.

How long does a custom antibody take?

It is set by the immunisation and screening schedule rather than the provider. Polyclonal projects are considerably shorter than monoclonal or recombinant ones, which add cloning, sequencing and expression.

What should the specification contain?

The target and the epitope region, what must be discriminated and what must be recognised across, the assay and sample type, the host and format, the screening format, and the acceptance criteria for validation.

How do I validate a custom antibody?

In the application it was commissioned for, with a real negative control such as a knockout, knockdown or non-expressing sample. A signal at the right size is not validation on its own.

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