Choosing CD marker antibodies for receptors that also bind antibodies: why a cd16 antibody and a cd32 antibody target Fc receptors that will capture your other reagents unless the panel blocks them first, what a cd64 antibody adds as the high affinity member, how a cd43 antibody, a cd59 antibody, a cd66b antibody, a cd71 antibody, a cd80 antibody, a cd83 antibody, a cd86 antibody, a cd90 antibody, a cd99 antibody, a cd122 antibody, a cd127 antibody, a cd161 antibody, a cd169 antibody, a cd200 antibody, a cd26 antibody, a cd2 antibody, a cd300a antibody, a cd41 antibody, a cd45rb antibody, a cd49d antibody, a cd61 antibody, a cd8a antibody, cd3 antibodies, cd4 antibodies, cd34 antibodies and a cd4 antibody flow cytometry panel each behave in fixation and in titration, where an nk1.1 antibody, an ly6c antibody, an nkg2a antibody, an nkg2c antibody, an nkg2d antibody, an icos antibody, a ccr6 antibody, a ccr7 antibody, a cxcr4 antibody, an xcr1 antibody, a batf3 antibody, a lilrb2 antibody and an fpr2 antibody sit in subset definition, and why clone identity matters more here than anywhere else

Building a surface panel

1. Block Fc receptors before staining. Cells carrying Fc receptors bind antibodies through the constant region, producing signal in every channel. A blocking reagent appropriate to the species goes on before the panel, and its absence is the commonest cause of an uninterpretable myeloid stain.
2. Record the clone, not the cluster. A cluster designation names an antigen, not a reagent. Two clones can recognise different epitopes with different accessibility, and switching clone is a protocol change requiring re titration.
3. Titrate on your own cells. The optimal amount is the one giving the best separation between positive and negative populations on your sample, and it is usually below the datasheet dilution. One titration per clone pays for itself immediately.
4. Match fluorophore brightness to antigen density. Low density antigens need bright fluorophores on clean detectors; high density lineage markers can sit anywhere. Getting this backwards is why panels underperform their design.
5. Check the epitope survives your processing. Enzymatic dissociation cleaves several surface antigens, and fixation destroys others. Where a marker matters, confirm with an alternative clone or a gentler protocol.

The clone is the reagent

Cluster designations were created so that reagents could be compared, and they succeeded well enough that people now treat the designation as the specification. It is not: the clone, its host, its fluorophore and its lot are the specification.

Record all four in the protocol. It is what lets a panel be rebuilt in another laboratory and what makes a discrepancy investigable.

Blocking is not optional

Fc receptor mediated binding affects exactly the populations most often studied, and it produces a plausible looking positive signal rather than obvious noise. That is what makes it dangerous.

Include the block in the standard protocol rather than as an option for difficult samples, and include an unstained and a fully blocked control when a new sample type is introduced.

Common questions

Why is everything positive in my myeloid stain?

Almost certainly unblocked Fc receptors. Add an appropriate blocking step before the panel and the background usually disappears entirely.

Are two clones against the same marker interchangeable?

No. They recognise different epitopes with different sensitivity to fixation and dissociation, and they frequently stain different fractions. Treat a clone change as a protocol change.

Should I use the datasheet dilution?

As a starting point only. Titration on your own cells almost always improves separation, and it is one plate of work per clone.

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