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Choose Your Flow Cytometry Workflow
Use this flow cytometry protocol guide to run antibody staining for surface markers, intracellular targets, phospho-flow signaling, or multicolor panels.
Surface staining flow cytometry protocol
Use this workflow for extracellular antigens on live or fixed cells before acquisition by flow cytometry.
- Use this format when: Detecting cell surface markers, receptors, lineage markers, or extracellular epitopes.
- Optimize first: Cell viability, Fc blocking, antibody amount, staining volume, wash conditions, and compensation controls.
1
Prepare single-cell suspension
Collect cells and make a single-cell suspension. Filter clumps if needed. Count cells and transfer 0.5-1 x 10^6 cells per tube or well. Keep cells on ice or at 4 degrees C when staining sensitive surface markers.
2
Wash cells
Add 1-2 mL staining buffer per tube, or 150-200 uL per 96-well plate well. Staining buffer can be PBS or HBSS with 1-2 percent FBS or BSA and 1-2 mM EDTA. Centrifuge 300-500 x g for 5 minutes and discard supernatant.
3
Block Fc receptors
Resuspend cells in 50-100 uL staining buffer containing Fc block or 5-10 percent normal serum when working with Fc receptor-positive cells. Incubate 10-15 minutes at 4 degrees C.
4
Add antibody
Add primary antibody at the datasheet-recommended flow cytometry amount or start with 0.25-1 ug per 10^6 cells for unconjugated antibody. For conjugated antibodies, use the recommended test size or titrate 0.125x, 0.25x, 0.5x, 1x, and 2x. Final staining volume is commonly 50-100 uL.
5
Incubate
Incubate 20-30 minutes at 4 degrees C protected from light. Mix gently halfway through if cells settle.
6
Wash
Add staining buffer, centrifuge 300-500 x g for 5 minutes, and discard supernatant. Wash 2 times. Resuspend final pellet in 200-500 uL staining buffer for acquisition.
7
Add secondary antibody if needed
If using an unconjugated primary antibody, add fluorophore-conjugated secondary antibody after the first wash. Incubate 20-30 minutes at 4 degrees C protected from light, then wash 2 times.
8
Acquire data
Filter samples if clumps are present. Acquire enough events for the population of interest. Use viability dye, unstained cells, single-color controls, fluorescence minus one controls, and isotype controls when appropriate.
Antibody titrationFlow cytometry antibody concentration should be titrated. Too much antibody can increase background without improving separation.
TemperatureCold staining reduces internalization of some surface receptors.
Intracellular flow cytometry protocol
Use this workflow for intracellular proteins, transcription factors, cytokines, or nuclear targets after fixation and permeabilization.
- Use this format when: The target is inside the cell or nucleus and requires membrane permeabilization.
- Optimize first: Fixation buffer, permeabilization buffer, antibody dilution, cell loss during washes, and intracellular controls.
1
Prepare and optionally stain surface markers
Prepare 0.5-1 x 10^6 cells per tube or well. If surface markers are also needed, stain surface antigens first using the surface staining protocol before fixation unless the surface antibody is fixation-resistant.
2
Fix cells
Add fixation buffer according to the kit or reagent instructions. A common starting condition is 1-4 percent paraformaldehyde for 10-20 minutes at room temperature. Wash with staining buffer.
3
Permeabilize
Resuspend cells in permeabilization buffer, such as saponin-based buffer for many cytoplasmic targets or methanol/permeabilization kit buffer for nuclear and phospho targets. Incubate 10-30 minutes as recommended.
4
Block
Incubate cells in permeabilization buffer containing 1-5 percent serum or BSA for 10-20 minutes. Keep cells in permeabilization buffer during antibody incubation and washes when using saponin-based systems.
5
Add primary antibody
Dilute primary antibody in permeabilization buffer. Start with the datasheet-recommended flow dilution or titrate 0.25-2 ug per 10^6 cells. Incubate 30-60 minutes at room temperature or 4 degrees C, protected from light when fluorophores are present.
6
Wash and add secondary if needed
Wash 2 times with permeabilization buffer. If the primary antibody is unconjugated, add fluorophore-conjugated secondary antibody for 20-30 minutes, then wash 2 times.
7
Resuspend and acquire
Resuspend cells in 200-500 uL staining buffer. Acquire samples promptly or store fixed stained cells at 4 degrees C protected from light for a short period if compatible with the fluorophores and assay.
Surface plus intracellular panelsConfirm that surface antibodies tolerate fixation and permeabilization before combining them with intracellular targets.
Cell lossUse low-retention tubes or V-bottom plates, and avoid harsh aspiration when working with limited samples.
Phospho-flow protocol
Use this workflow for phosphorylation or signaling-state analysis by flow cytometry.
- Use this format when: Measuring pathway activation, inhibitor response, stimulation kinetics, or modification-specific intracellular signal.
- Optimize first: Stimulation timing, fixation speed, methanol compatibility, antibody titration, and positive or inhibited controls.
1
Prepare stimulation plan
Set up untreated, stimulated, inhibited, and positive control samples. Time stimulation carefully because phosphorylation can change within minutes.
2
Fix immediately
At each time point, fix cells quickly to preserve signaling state. Add pre-warmed fixation buffer to reach the recommended final concentration, commonly 1-4 percent paraformaldehyde, and incubate 10-15 minutes.
3
Permeabilize
Wash cells, then permeabilize using cold 90 percent methanol added slowly while vortexing gently, or use a phospho-flow permeabilization kit. Incubate on ice or at -20 degrees C for 10-30 minutes depending on the protocol.
4
Rehydrate and block
Wash cells 2 times with staining buffer to remove methanol. Block in staining buffer with 1-5 percent BSA or serum for 10-20 minutes.
5
Add phospho/PTM antibody
Dilute primary antibody in staining buffer. Use the datasheet-recommended flow dilution or titrate across a range. Incubate 30-60 minutes at room temperature or 4 degrees C.
6
Wash and detect
Wash 2 times. Add fluorescent secondary antibody if needed and incubate 20-30 minutes protected from light. Wash again and resuspend for acquisition.
7
Acquire and analyze
Use unstimulated and stimulated controls to set gates. Compare median fluorescence intensity rather than percent positive when signal shifts are continuous.
Methanol sensitivitySome surface fluorophores and epitopes do not tolerate methanol. Stain methanol-sensitive surface markers after permeabilization only if compatible, or choose resistant clones/fluorophores.
KineticsRun pilot time courses when measuring signaling events.
Multicolor flow cytometry panel protocol
Use this workflow to combine multiple antibody markers in one flow cytometry panel.
- Use this format when: Multiple cell populations or markers need to be measured in the same sample.
- Optimize first: Fluorophore brightness, marker density, spillover, antibody titration, compensation controls, and fluorescence minus one controls.
1
Design panel
Assign bright fluorophores to low-abundance markers and dimmer fluorophores to high-abundance markers. Avoid placing highly co-expressed markers in channels with severe spillover.
2
Titrate each antibody
Titrate each antibody individually using the same cell type and staining conditions planned for the experiment. Choose the lowest antibody amount that gives clear separation with acceptable background.
3
Prepare cells and Fc block
Aliquot 0.5-1 x 10^6 cells per sample. Wash and block Fc receptors for 10-15 minutes at 4 degrees C.
4
Add antibody cocktail
Prepare a master mix containing all antibodies at final optimized concentrations. Include primary antibody if it is part of the panel. Add the cocktail to cells in 50-100 uL final staining volume and incubate 20-30 minutes at 4 degrees C protected from light.
5
Wash and fix if needed
Wash 2 times with staining buffer. Fix cells if required by biosafety policy or if acquisition will be delayed. Confirm that fluorophores tolerate fixation.
6
Prepare controls
Prepare unstained cells, single-color compensation controls, viability-only control, and fluorescence minus one controls for critical gates. Include biological positive and negative controls when available.
7
Acquire and gate
Acquire enough events for rare populations. Use compensation controls to correct spillover and FMO controls to place gates for dim or continuous markers.
Panel complexityA good 4-color panel with strong controls is more useful than an overloaded panel with poor compensation.
Viability dyeInclude a viability dye when dead cells could increase nonspecific antibody binding.
Flow cytometry reference notes
Sample qualityFlow cytometry depends on clean single-cell suspensions. Clumps, dead cells, debris, low viability, and harsh dissociation can create false signal and poor gates.
Antibody titrationTitrate antibodies rather than relying only on a generic volume. A good staining concentration gives strong separation with low background and minimal spillover into other channels.
ControlsUse unstained cells, single-color controls, FMO controls, viability controls, and biological positive/negative controls as needed. Compensation controls should match the fluorophores used in the panel.
Fixation compatibilitySome epitopes and fluorophores are sensitive to fixation or methanol. Confirm whether the antibody is intended for live surface staining, fixed cells, intracellular staining, or phospho-flow.
Common problemsPoor separation can come from excess antibody, weak antigen expression, poor compensation, autofluorescence, dead cells, Fc receptor binding, or incompatible fixation/permeabilization.
Use these conditions as practical starting points. Follow the product datasheet, kit manual, safety data sheet, and institutional safety requirements when they provide application-specific instructions.
