Question 5 of 6 Intermediate Scenario

How would you design a flow panel with coexpressed markers?

Short answer

Assign bright dyes to dim, important markers and avoid pairs whose spillover spreading undermines resolution when both markers occur on the same cells. Consider antigen abundance, fluorochrome spectra, instrument optics, clone performance and controls before finalizing the panel.

Why

List the cell populations and smallest effects the assay needs to resolve. For each antigen, estimate expression intensity, density, coexpression and whether the readout is continuous or binary. Inspect available lasers, detectors and the instrument-specific spillover spreading matrix.

For example, if two dim activation markers are coexpressed, placing one near a very bright fluorochrome with heavy spillover spread may hide subtle positivity even with correct compensation. Select bright clean channels for those dim markers, and place abundant lineage markers in less sensitive channels if needed. Titrate every antibody, check tandem-dye behavior and account for autofluorescence in relevant tissues.

Use single-color references, appropriate FMOs and actual positive controls in a pilot run. Reevaluate after panel expansion because adding just one dye changes how negative populations spread. Optimize for resolution of the scientific question rather than maximizing the number of fluorochromes.

Common mistakes

Confusing mathematically corrected mean spillover with zero spread, or assigning dyes only by brightness

The interviewer might ask next

How would you modify the panel if dim PD-1 and TIM-3 cannot be separated in coexpressing cells?