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ABMIUM laboratory protocol
A complete flow cytometry protocol covering sample preparation, controls, viability, surface and intracellular staining, acquisition, gating and troubleshooting.
Application overview | Download linked PDF | Browse flow cytometry antibodies | Ask technical support
Flow cytometry is a high-throughput technique that measures the physical and fluorescence characteristics of individual cells as they pass through one or more laser beams in a fluid stream. By combining multiple fluorophore-conjugated antibodies, researchers can simultaneously detect and quantify surface and intracellular markers on thousands of cells per second.
This protocol covers the complete workflow for multiparameter immunophenotyping of single-cell suspensions, including surface staining, viability discrimination, and intracellular staining where required. It is compatible with peripheral blood mononuclear cells (PBMCs), whole blood, tissue culture cells, and dissociated solid tissues.
This protocol supports both direct (fluorophore-conjugated primary antibody) and indirect (unlabeled primary + labeled secondary) detection methods. Intracellular staining requires fixation and permeabilization steps as indicated.
Overview of Flow Cytometry Procedure (Created with BioRender)
Equipment required
Instrumentation
Flow cytometer (≥2 lasers recommended for multicolor panels)
Refrigerated centrifuge
Hemocytometer or automated cell counter
Vortex mixer
Adjustable pipettes (2 - 1000 µ1L)
Water bath or heat block (37 °C)
Consumables
Polystyrene round-bottom tubes (12 × 75 mm)
96-well U-bottom plate (optional, high-throughput)
Cell strainer, 40 - 70 µM mesh
Microcentrifuge tubes (1.5 mL)
Sterile serological pipettes
Gloves, lab coat, and eye protection
Reagents required
Buffers and solutions
Phosphate-buffered saline (PBS), pH 7.4, without calcium or magnesium
Flow cytometry staining buffer: PBS + 2 - 5% fetal calf serum (FCS) or 1% BSA + 0.02% sodium azide
RBC lysis buffer (e.g., ammonium chloride-based, 1×)
Fixation solution: 1 - 4% paraformaldehyde (PFA) in PBS
Permeabilization buffer (saponin-based, 0.1% non-ionic detergent)
Fc receptor blocking reagent (species-specific)
Antibodies and dyes
Fluorophore-conjugated primary antibodies, pre-titrated for your panel
Viability dye (e.g., SYTOX, DAPI, or fixable Live/Dead stain)
Single-color compensation controls (antibody-capture beads or cells)
Fluorescence minus one (FMO) controls for each channel
Isotype control antibodies (matched to primary antibody isotype)
Sample preparation
The goal is a homogeneous single-cell suspension at 1 - 10 × 10⁶ cells/mL, free of clumps and debris. Preparation method depends on the sample source:
Suspension cultures
Transfer cells to centrifuge tube
Centrifuge at 300 - 400 × g, 5 min, 4 °C
Discard supernatant; resuspend pellet in cold PBS
Repeat wash; resuspend in staining buffer
Count and assess viability (Trypan Blue or automated)
Adherent cultures
Aspirate medium; wash twice with PBS
Detach with enzyme-free dissociation buffer or gentle scraping (enzymatic dissociation can alter surface epitopes)
Neutralize and centrifuge at 300 × g, 5 min
Resuspend in staining buffer; filter through 40 µM strainer
Whole blood
Process within 4 h of collection
Stain with antibody panel directly on 100 µL whole blood
Lyse RBCs after staining using 1× lysis buffer (10 min, RT)
Centrifuge 300 × g, 5 min; wash twice with PBS
Resuspend in staining buffer for acquisition
Solid tissues
Mince tissue into 1 - 2 mm pieces in cold PBS
Digest enzymatically (collagenase D + DNase I, 37 °C, 30 - 45 min) or dissociate mechanically
Filter through 70 µM strainer; wash with PBS
Lyse RBCs if needed; count viable cells
Prepare instrument and controls
Count cells with a hemocytometer or automated counter. Assess viability with Trypan Blue. Adjust to 1 - 10 × 10⁶ cells/mL in staining buffer. Aliquot 1 × 10⁶ cells per staining tube (100 µL volume).
Add species-matched Fc blocking reagent to each tube. Incubate 5 - 10 min at 4 °C. Do not wash after blocking - add antibody cocktail directly to maintain Fc block during staining.
For non-fixable assays: add impermeant viability dye (e.g., SYTOX Green) to the antibody cocktail. For assays requiring fixation: use a fixable Live/Dead stain - incubate 15 - 20 min at 4 °C in PBS without serum (serum quenches amine-reactive dyes).
Add a pre-titrated fluorophore-conjugated antibody cocktail (total volume 100 µL per tube) and mix gently. Incubate 20 - 30 min at 4 °C in the dark. Wash twice with 2 mL cold staining buffer at 300 × g for 5 min. Remove supernatant completely between washes.
Resuspend cells in 200 - 500 µL of 1 - 2% PFA in PBS. Incubate 10 - 20 min at room temperature. Wash once with a staining buffer. Store at 4 °C in the dark and acquire within 24 - 48 h. Skip to Step 8 if analyzing immediately without fixation.
After surface staining and washing, fix cells with 4% PFA for 20 min at RT. Wash twice with PBS. Permeabilize with 0.1% saponin-based buffer for 15 min at RT. Incubate intracellular antibody cocktail in permeabilization buffer (maintain saponin throughout) for 30 - 60 min at 4 °C in the dark.
Wash cells twice with a staining buffer at 300 × g for 5 min. Resuspend in 300 - 500 µL of staining buffer or PBS. Filter through a 35 - 40 µM strainer cap into acquisition tubes to remove clumps.
Acquire at least 10,000 - 50,000 events per sample (increase to 100,000+ for rare populations). Record FSC/SSC and all fluorescence channels. Collect single-stained controls for compensation matrix calculation. Run samples at low to medium flow rate to maximize data quality.
Apply spectral compensation matrix. Gate sequentially: debris exclusion (FSC/SSC) → doublet discrimination (FSC-H vs FSC-A) → live/dead discrimination → population of interest. Use FMO controls to define positive/negative boundaries. Export in FCS format and analyze with FlowJo, FCS Express, or equivalent.
Limitations
Flow cytometry requires single-cell suspensions - unsuitable for direct analysis of intact tissues or adherent monolayers without prior dissociation.
No spatial context is preserved; unlike imaging techniques, the relative positions of cells within tissue architecture are lost.
Spectral overlap between fluorophores limits the number of parameters that can be simultaneously measured on conventional instruments without spectral unmixing.
Fixation and permeabilization can denature protein-based fluorophores (PE, APC) when alcohol-based solvents are used; avoid these with such fluorophores.
Aldehyde-based fixatives (PFA, formaldehyde) generate autofluorescent by-products - prefer fluorophores with longer emission wavelengths (>550 nm) for fixed samples.
Rare populations (<0.1%) require very high event counts and optimized gating strategies; misidentification risk increases without proper controls.
Data quality is operator-dependent; inconsistent sample handling, antibody lot variation, or instrument drift between sessions can introduce confounding variability.
Enzyme-based tissue dissociation can cleave or modify cell surface epitopes, potentially reducing antibody binding efficiency for certain markers.
Troubleshooting
Flow cytometry enables rapid, high-throughput single-cell analysis for multiparameter immunophenotyping. It allows simultaneous detection of surface and intracellular markers, supporting cell viability assessment, immune profiling, and functional studies across samples such as blood, cultured cells, and tissues.
Products and support for this protocol
Browse flow cytometry antibodies. Confirm application validation, species reactivity, sample type and detection requirements before selection.
Contact ABMIUM scientific support for product selection and troubleshooting.
For research use only. This protocol is general guidance and does not replace product-specific instructions, institutional safety procedures or local risk assessments.
ABMIUM laboratory protocol
A complete flow cytometry protocol covering sample preparation, controls, viability, surface and intracellular staining, acquisition, gating and troubleshooting.
Application overview | Download linked PDF | Browse flow cytometry antibodies | Ask technical support
Flow cytometry is a high-throughput technique that measures the physical and fluorescence characteristics of individual cells as they pass through one or more laser beams in a fluid stream. By combining multiple fluorophore-conjugated antibodies, researchers can simultaneously detect and quantify surface and intracellular markers on thousands of cells per second.
This protocol covers the complete workflow for multiparameter immunophenotyping of single-cell suspensions, including surface staining, viability discrimination, and intracellular staining where required. It is compatible with peripheral blood mononuclear cells (PBMCs), whole blood, tissue culture cells, and dissociated solid tissues.
This protocol supports both direct (fluorophore-conjugated primary antibody) and indirect (unlabeled primary + labeled secondary) detection methods. Intracellular staining requires fixation and permeabilization steps as indicated.
Overview of Flow Cytometry Procedure (Created with BioRender)
Equipment required
Instrumentation
Flow cytometer (≥2 lasers recommended for multicolor panels)
Refrigerated centrifuge
Hemocytometer or automated cell counter
Vortex mixer
Adjustable pipettes (2 - 1000 µ1L)
Water bath or heat block (37 °C)
Consumables
Polystyrene round-bottom tubes (12 × 75 mm)
96-well U-bottom plate (optional, high-throughput)
Cell strainer, 40 - 70 µM mesh
Microcentrifuge tubes (1.5 mL)
Sterile serological pipettes
Gloves, lab coat, and eye protection
Reagents required
Buffers and solutions
Phosphate-buffered saline (PBS), pH 7.4, without calcium or magnesium
Flow cytometry staining buffer: PBS + 2 - 5% fetal calf serum (FCS) or 1% BSA + 0.02% sodium azide
RBC lysis buffer (e.g., ammonium chloride-based, 1×)
Fixation solution: 1 - 4% paraformaldehyde (PFA) in PBS
Permeabilization buffer (saponin-based, 0.1% non-ionic detergent)
Fc receptor blocking reagent (species-specific)
Antibodies and dyes
Fluorophore-conjugated primary antibodies, pre-titrated for your panel
Viability dye (e.g., SYTOX, DAPI, or fixable Live/Dead stain)
Single-color compensation controls (antibody-capture beads or cells)
Fluorescence minus one (FMO) controls for each channel
Isotype control antibodies (matched to primary antibody isotype)
Sample preparation
The goal is a homogeneous single-cell suspension at 1 - 10 × 10⁶ cells/mL, free of clumps and debris. Preparation method depends on the sample source:
Suspension cultures
Transfer cells to centrifuge tube
Centrifuge at 300 - 400 × g, 5 min, 4 °C
Discard supernatant; resuspend pellet in cold PBS
Repeat wash; resuspend in staining buffer
Count and assess viability (Trypan Blue or automated)
Adherent cultures
Aspirate medium; wash twice with PBS
Detach with enzyme-free dissociation buffer or gentle scraping (enzymatic dissociation can alter surface epitopes)
Neutralize and centrifuge at 300 × g, 5 min
Resuspend in staining buffer; filter through 40 µM strainer
Whole blood
Process within 4 h of collection
Stain with antibody panel directly on 100 µL whole blood
Lyse RBCs after staining using 1× lysis buffer (10 min, RT)
Centrifuge 300 × g, 5 min; wash twice with PBS
Resuspend in staining buffer for acquisition
Solid tissues
Mince tissue into 1 - 2 mm pieces in cold PBS
Digest enzymatically (collagenase D + DNase I, 37 °C, 30 - 45 min) or dissociate mechanically
Filter through 70 µM strainer; wash with PBS
Lyse RBCs if needed; count viable cells
Prepare instrument and controls
Count cells with a hemocytometer or automated counter. Assess viability with Trypan Blue. Adjust to 1 - 10 × 10⁶ cells/mL in staining buffer. Aliquot 1 × 10⁶ cells per staining tube (100 µL volume).
Add species-matched Fc blocking reagent to each tube. Incubate 5 - 10 min at 4 °C. Do not wash after blocking - add antibody cocktail directly to maintain Fc block during staining.
For non-fixable assays: add impermeant viability dye (e.g., SYTOX Green) to the antibody cocktail. For assays requiring fixation: use a fixable Live/Dead stain - incubate 15 - 20 min at 4 °C in PBS without serum (serum quenches amine-reactive dyes).
Add a pre-titrated fluorophore-conjugated antibody cocktail (total volume 100 µL per tube) and mix gently. Incubate 20 - 30 min at 4 °C in the dark. Wash twice with 2 mL cold staining buffer at 300 × g for 5 min. Remove supernatant completely between washes.
Resuspend cells in 200 - 500 µL of 1 - 2% PFA in PBS. Incubate 10 - 20 min at room temperature. Wash once with a staining buffer. Store at 4 °C in the dark and acquire within 24 - 48 h. Skip to Step 8 if analyzing immediately without fixation.
After surface staining and washing, fix cells with 4% PFA for 20 min at RT. Wash twice with PBS. Permeabilize with 0.1% saponin-based buffer for 15 min at RT. Incubate intracellular antibody cocktail in permeabilization buffer (maintain saponin throughout) for 30 - 60 min at 4 °C in the dark.
Wash cells twice with a staining buffer at 300 × g for 5 min. Resuspend in 300 - 500 µL of staining buffer or PBS. Filter through a 35 - 40 µM strainer cap into acquisition tubes to remove clumps.
Acquire at least 10,000 - 50,000 events per sample (increase to 100,000+ for rare populations). Record FSC/SSC and all fluorescence channels. Collect single-stained controls for compensation matrix calculation. Run samples at low to medium flow rate to maximize data quality.
Apply spectral compensation matrix. Gate sequentially: debris exclusion (FSC/SSC) → doublet discrimination (FSC-H vs FSC-A) → live/dead discrimination → population of interest. Use FMO controls to define positive/negative boundaries. Export in FCS format and analyze with FlowJo, FCS Express, or equivalent.
Limitations
Flow cytometry requires single-cell suspensions - unsuitable for direct analysis of intact tissues or adherent monolayers without prior dissociation.
No spatial context is preserved; unlike imaging techniques, the relative positions of cells within tissue architecture are lost.
Spectral overlap between fluorophores limits the number of parameters that can be simultaneously measured on conventional instruments without spectral unmixing.
Fixation and permeabilization can denature protein-based fluorophores (PE, APC) when alcohol-based solvents are used; avoid these with such fluorophores.
Aldehyde-based fixatives (PFA, formaldehyde) generate autofluorescent by-products - prefer fluorophores with longer emission wavelengths (>550 nm) for fixed samples.
Rare populations (<0.1%) require very high event counts and optimized gating strategies; misidentification risk increases without proper controls.
Data quality is operator-dependent; inconsistent sample handling, antibody lot variation, or instrument drift between sessions can introduce confounding variability.
Enzyme-based tissue dissociation can cleave or modify cell surface epitopes, potentially reducing antibody binding efficiency for certain markers.
Troubleshooting
Flow cytometry enables rapid, high-throughput single-cell analysis for multiparameter immunophenotyping. It allows simultaneous detection of surface and intracellular markers, supporting cell viability assessment, immune profiling, and functional studies across samples such as blood, cultured cells, and tissues.
Products and support for this protocol
Browse flow cytometry antibodies. Confirm application validation, species reactivity, sample type and detection requirements before selection.
Contact ABMIUM scientific support for product selection and troubleshooting.
For research use only. This protocol is general guidance and does not replace product-specific instructions, institutional safety procedures or local risk assessments.