selection guide
Panel design starts with the biology
Which biology, antigen density and spillover rules to name before you assign fluorophores or request a cytometer configuration.
- Author
- EVRINTH Editorial Team
- Published
- 8 October 2026
- Updated
- 8 October 2026
- Reading time
- 7 min
Write the populations you must separate before you write the colours. The decision this page supports is which criteria a panel specification should name so that fluorophore assignment follows the biology, the antigen density and the spillover the instrument will actually collect. How those colours become pulses is described in how a flow cytometer reads a cell.
Layouts you can compare sit in the scientific instruments catalogue. The assay's place in a wider workflow is the molecular biology pathway. The laser and filter list belongs in a quote request.
The biological sentence comes first
A panel is a set of measurements that can support one comparison. Write that comparison in ordinary language: which population, in which parent, relative to which control, on which day of treatment. Every marker you add must serve that sentence or serve a gate the sentence depends on. Lineage markers, a viability dye, and a dump of cells you must exclude are there so the numerator is clean. Markers added because the conjugate was available do not make the sentence stronger. They add spillover and they add tubes that can fail.
Name co-expression explicitly. If two markers must be resolved on the same cell, their fluorophores cannot be a pair that the filter set cannot separate, and their spreading cannot bury the dimmer of the two. If two markers are mutually exclusive and only used as dumps, they can share more overlap because you will not call a double-positive between them. That distinction is biology. It is also the cheapest way to spend your difficult detector pairs.
Gating order belongs in the same paragraph. Parent, then viability, then doublets, then lineage, then the question. A specification that lists antibodies and never lists the parent population will be analysed in as many ways as there are readers.
Antigen density and fluorophore brightness
Antigens are not equally abundant. Some lineage molecules are dense enough that a modest fluorophore still pulls the positive population clear of the negative. Some receptors, transcription factors and phospho-epitopes are sparse. Those need a bright fluorophore class, a detector with low background, and neighbours that do not dump spread into that detector.
Brightness here means photons collected per antibody, in that optical window, not the colour name on the vial. Classical protein fluorophores such as the PE and APC classes are often among the brighter choices on instruments that excite them well. A dye that is bright on one laser can be dim on another. Match the excitation to the laser you have. A "red" label that your red laser barely excites is a dim dye, however it looks in a catalogue photograph.
Reserve the brightest, cleanest detectors for the lowest-density antigens that drive the conclusion. Put bright, spreading dyes on high-density markers you only need as a yes-or-no gate, and keep them spectrally away from the dim question. If the only bright dye left for the dim antigen sits next to a spreading dump, change the dump colour or drop a marker. A panel that cannot see its own question is not saved by acquiring more events.
Spillover spreading is a design input
Compensation will subtract the median overlap. It will not narrow the widened negative that a bright neighbour causes. That widening is spillover spreading, and it is predictable in direction even before you have stained: a dye with a long emission tail into the question detector will spread there in proportion to how bright it is. Design as if that spread is a cost.
Ask, for each dim channel, which other fluorophores will be present and whether they are expected to be extremely bright. A highly expressed marker on a tandem with a messy tail is a common way to lose a dim cytokine or a dim receptor. Swap assignments on paper before you conjugate or buy the set. Single-stain controls still have to be run. Design reduces how often those controls tell you to start over.
Fixation and permeabilisation are design inputs too. Some fluorophores, especially some tandems and fluorescent proteins, do not survive the fixative or the alcohol step the clone requires. Read the antibody sheet for the clone, not for the antigen in the abstract. A surface marker that must be stained before fixation occupies a tube order, and that order belongs in the specification.
What the instrument specification must name
Lasers: which lines, not only how many. Filters: centre and width, or the manufacturer's band, for each detector. Detectors: enough simultaneous channels for the panel, including viability. Sample format: tube or plate, because a plate loader changes how you design controls and how long cells wait. Software: whether it stores an FCS file with the spillover matrix and the parameter names. None of these is a brand preference. Each one decides whether a dye assignment is real.
| Criterion | What to write down | If you leave it out |
|---|---|---|
| Biological comparison | Parent population, question marker, control | The panel answers a different question than the one you publish |
| Antigen density class | High, intermediate or low for each marker | Bright dyes get wasted on easy lineages |
| Fluorophore brightness on this optical path | Which laser excites it and which filter collects it | A dye looks bright in the vial and dim in the file |
| Spillover into the dim channel | Which bright markers are allowed to neighbour it | Spread swallows the positive you care about |
| Fix and perm constraints | Clone sheet requirement, dye survival | The colour is gone after the intracellular step |
| Controls | Single stains at sample brightness, unstained, fluorescence-minus-one | Gates move with nobody able to say why |
When a draft panel fails
If the fluorescence-minus-one control for the dim marker overlaps the positive you expected, the design has a spreading or density problem. Swapping fluorophores is the branch. Raising voltage until the overlap looks like two peaks usually saturates a neighbour and breaks compensation. If a tandem looks bright in the donor channel and dim in its own, the tandem has degraded. Replace the lot. Do not design around a broken reagent by calling the donor channel a second colour.
If the instrument lacks the laser the dye needs, stop. Another antibody clone on a dye you can excite is a redesign. Acquiring the wrong laser's file and compensating harder does not create excitation. Write the failed assignment in the specification notes so the next panel does not repeat it under a new sample name.
Safety and research limits
Panel design does not decide whether the cells may be run. Unfixed human or infectious material stays with the institutional assessment, using the WHO Laboratory biosafety manual and the CDC BMBL as references rather than as a permit from this page. A well-built panel is still a research comparison. It is not a diagnostic panel. The International Society for Advancement of Cytometry hosts the community discussion of reporting standards such as minimum information for a flow experiment. Citing that community is not a claim that your panel has been reviewed.
What to send with an enquiry
Send the biological sentence, the number of markers that must be simultaneous, the lasers you already depend on, whether you need intracellular staining, and whether the format is tube or plate. Ask for filter bands and for confirmation that the software exports the matrix. Use the scientific instruments catalogue and the quote request. Ask whether a quotation is possible. A channel count without the biology is not a panel.
Questions from the bench
Should the brightest fluorophore go on the most important marker?
Put brightness where the antigen is scarce. A high-density lineage marker can carry a dimmer fluorophore and still separate. A low-density antigen on the same cells will disappear if it is given a dim dye or if a bright neighbour spills spread into its channel. Importance to the question and brightness of the dye meet at antigen density, not at a ranking of how exciting the marker sounds.
What should a specification say about spreading?
Name the dim channel you must resolve and the bright channels allowed to spill into it. A configuration can be rejected when the only available filter pair puts a very bright, broadly emitting dye next to that dim question. The specification should ask for laser lines, filter bands and a software path that stores the spillover matrix. A colour count without those bands hides the conflict.
Do I design the panel before I know the instrument?
You can write the biology first anywhere. You can assign dyes only after you know the lasers and filters. Designing a six-colour panel on dyes your cytometer cannot excite wastes the antibody conjugation. Write the biology, then lock the optical layout, then assign fluorophores, then order the controls.
Where do viability and dump channels fit?
They are part of the biology: dead cells and unwanted lineages will otherwise occupy the rare gate. Give them fluorophores that can be bright, and keep their spreading away from the dimmest positive you need to call. A dump channel that spreads into the question channel costs more than it saves. Place it on a detector the question does not use.
References
Manufacturer names identify published method classes. Trademarks remain with their owners. Catalogue records on this site are independent references for enquiry. They are not a statement of inventory, distribution rights or a supply commitment. This page is educational. It is not medical advice, a diagnostic protocol or a biosafety approval.
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How a flow cytometer reads a cellHow a cytometer focuses cells into a laser, turns scatter and fluorescence into pulses, and why a gate is an argument rather than a fact.A glossary of optical measurementsWhich optical measurements a microscope or cytometer specification should name so a later user can repeat the light path.Biosafety of unfixed human samplesWhy unfixed human blood, tissue and cells on a cytometer or microscope stay an institutional biosafety decision, not a technique choice.