This protocol removes erythrocytes from rodent blood samples while preserving nucleated cells for flow cytometry, immunophenotyping, and cellular analyses. The procedure uses lysis buffer to selectively lyse red blood cells while maintaining leukocyte viability and function. By the end of this procedure, you should have a clean suspension of nucleated cells ready for downstream applications with >90% viability.
What is Red Blood Cell Lysis?
Red blood cell lysis serves as an essential sample preparation technique for researchers studying hematopoietic cells, immune responses, and cellular therapies in rodent models. This standardized procedure removes the overwhelming population of erythrocytes that can interfere with flow cytometric analysis and obscure target cell populations of interest. The technique enables accurate immunophenotyping, cell sorting, and functional assays by eliminating red blood cells that lack nuclei and express limited surface markers. Researchers assess readiness by confirming proper anticoagulant use during blood collection, appropriate sample volumes per institutional guidelines, and access to validated lysis reagents.
Prerequisites
- Basic knowledge of aseptic technique and cell handling
- Understanding of blood collection methods approved by IACUC
- Familiarity with centrifugation and cell counting procedures
- Access to appropriate laboratory equipment and reagents
- Institutional Animal Care and Use Committee (IACUC) approval for blood collection protocols
Objectives
- Remove red blood cells from rodent blood samples using selective lysis
- Preserve nucleated cell populations with high viability (>90%)
- Prepare clean cell suspensions suitable for flow cytometry and immunophenotyping
- Generate consistent results across multiple samples and experimental sessions
- Optimize cell recovery rates for downstream analytical applications
Duration
00:45:00 (including sample preparation, lysis procedure, washing steps, and cell counting)
Estimated Cost
$145 USD (assuming purchase of reagents and consumables for 50 samples)
Supplies
- Red blood cell lysis buffer (commercial or ACK buffer prepared fresh)
- Phosphate-buffered saline (PBS), pH 7.4, sterile
- Complete medium with 2% fetal bovine serum
- 15 mL conical centrifuge tubes, sterile
- Serological pipettes (5 mL, 10 mL, 25 mL)
- Micropipette tips (1000 μL, 200 μL)
- Disposable nitrile gloves
- Paper towels for cleanup
- Waste containers for biological disposal
Tools
- Centrifuge capable of 300-500 x g with temperature control
- Micropipettes (P1000, P200)
- Hemocytometer or automated cell counter
- Inverted microscope for cell visualization
- Timer with second precision
- Vortex mixer for sample resuspension
- Ice bucket for sample storage
Materials
Rodent blood samples (collected with EDTA, heparin, or citrate anticoagulant), trypan blue solution for viability assessment, cell counting chambers, laboratory notebooks for data recording
Protocol
Step 1: Prepare Lysis Buffer and Workspace
Prepare fresh ACK lysis buffer (150 mM NH₄Cl, 10 mM KHCO₃, 0.1 mM EDTA, pH 7.2-7.4) or use commercial RBC lysis buffer according to manufacturer specifications. Verify buffer pH using calibrated pH meter and adjust if necessary to maintain optimal lysis conditions. Set up workspace in biosafety cabinet with all required materials within easy reach. Pre-chill centrifuge to 4°C and ensure PBS is at appropriate temperature. Label all tubes clearly with sample identification and experimental details for proper tracking throughout the procedure.
Step 2: Document Sample Information
Record detailed sample information including animal identification, collection method, anticoagulant used, collection volume, and time from collection to processing in laboratory notebooks. Document any visible abnormalities in blood appearance including unusual coloration, clotting, or hemolysis that occurred during collection. Weigh or measure sample volume accurately to ensure proper lysis buffer ratios. This documentation ensures compliance with institutional protocols and enables troubleshooting if unexpected results occur during processing.
Step 3: Perform Initial Cell Assessment
Transfer blood sample to 15 mL conical tube and examine visually for clots or unusual appearance that might affect lysis efficiency. If using whole blood, dilute 1:1 with PBS to reduce viscosity and improve lysis buffer access to cells. Perform initial cell count using hemocytometer to document starting cell numbers and calculate expected yield after processing. Record red blood cell to white blood cell ratio for protocol optimization and quality control purposes.
Step 4: Execute Red Blood Cell Lysis
Add lysis buffer to blood sample at 10:1 ratio (10 mL buffer per 1 mL blood sample) and mix gently by inversion 5-6 times to ensure complete distribution. Incubate at room temperature for 2-5 minutes for rodent samples while monitoring color change from red to clear or pale pink indicating successful RBC lysis. Avoid over-incubation beyond 5 minutes for rodent blood as this can damage target nucleated cells and reduce viability. Mix samples gently every 1-2 minutes during incubation to maintain consistent lysis conditions throughout the sample volume.
Step 5: Neutralize and Wash Cells
Add equal volume of PBS containing 2% fetal bovine serum to stop the lysis reaction and protect remaining cells from osmotic stress. Centrifuge samples at 300-500 x g for 5 minutes at 4°C to pellet nucleated cells while removing lysed RBC debris in supernatant. Carefully aspirate supernatant without disturbing the cell pellet, leaving approximately 200 μL to avoid cell loss. Resuspend pellet in 5 mL PBS and repeat centrifugation and washing steps once more to remove residual lysis buffer and cellular debris.
Step 6: Prepare Final Cell Suspension
Resuspend final cell pellet in appropriate volume of complete medium or PBS based on downstream application requirements. Perform cell count and viability assessment using trypan blue exclusion method to ensure >90% viability for healthy samples. Calculate total cell recovery and yield compared to initial cell numbers for quality control documentation. Adjust cell concentration as needed for specific experimental protocols, typically 1-5 x 10⁶ cells/mL for flow cytometry applications.
Step 7: Quality Control and Documentation
Examine cell suspension under inverted microscope to confirm absence of red blood cells and presence of intact nucleated cells with normal morphology. Document any remaining RBC contamination or unusual cell appearance that might require protocol modification. Record final cell count, viability percentage, and total yield in laboratory notebooks with clear sample identification. Store processed samples on ice if immediate use is not planned, but process within 2-4 hours for optimal cell function and viability.
Analyze the Results
Cell Recovery and Viability Assessment
Calculate cell recovery rate by comparing final nucleated cell count to initial white blood cell count from whole blood samples. Normal recovery rates range from 70-85% for healthy samples processed under optimal conditions. Assess cell viability using trypan blue exclusion method with acceptance criteria of >90% viable cells for downstream applications. Document any samples falling below quality thresholds and investigate potential causes including extended processing time, inappropriate buffer pH, or over-lysis conditions.
Purity Evaluation Methods
Examine processed samples microscopically to confirm complete or near-complete removal of red blood cells while preserving nucleated cell populations. Residual RBC contamination should be <5% of total cells for most applications, with complete absence preferred for flow cytometry. Calculate purity index by determining percentage of nucleated cells versus total cells in final suspension. Consider additional washing steps or modified lysis conditions for samples not meeting purity requirements.
Troubleshooting
Incomplete Red Blood Cell Lysis
Incomplete lysis typically results from insufficient incubation time, improper buffer pH, or inadequate buffer-to-sample ratios that prevent effective membrane disruption. Extend incubation time by 1-2 minutes for rodent samples while monitoring sample color change, or increase lysis buffer volume to 15:1 ratio for samples with high hematocrit. Verify buffer pH remains between 7.2-7.4 and prepare fresh buffer if stored reagents show pH drift. Consider using commercial lysis buffers if homemade preparations consistently produce suboptimal results.
Low Cell Viability After Processing
Reduced viability often indicates over-lysis from extended incubation times, improper buffer osmolarity, or temperature fluctuations during processing. Reduce incubation time to 2-3 minutes for rodent samples and ensure samples remain at room temperature throughout lysis procedure. Add neutralization buffer (PBS with serum) immediately after optimal lysis time to prevent continued cell damage. Verify that all buffers maintain proper pH and osmolarity specifications through regular quality control testing.
Poor Cell Recovery Rates
Low recovery rates may result from excessive centrifugation speeds, incomplete resuspension of cell pellets, or cell loss during aspiration steps. Use centrifugation speeds within the 300-500 x g range and extend time to 6-7 minutes for gentler pelleting conditions. Ensure complete pellet resuspension using gentle pipetting or brief vortexing before each wash step. Leave small volume of supernatant (100-200 μL) during aspiration to prevent inadvertent cell removal with debris.
Persistent Red Blood Cell Contamination
Continuing RBC presence may indicate inadequate lysis buffer preparation, expired reagents, or samples with unusually high hematocrit requiring modified protocols. Prepare fresh lysis buffer and verify pH accuracy using calibrated equipment before processing additional samples. Consider sequential lysis treatments with fresh buffer for samples showing resistance to standard protocols. Increase buffer volume ratio to 15:1 or 20:1 for samples with elevated red blood cell concentrations.
Data Analysis and Interpretation
Analyze cell processing data using spreadsheet software to track recovery rates, viability percentages, and purity metrics across experimental sessions. Calculate mean recovery rates and standard deviations for quality control trending and protocol optimization. Generate process control charts to identify systematic variations that might require protocol adjustments or equipment maintenance. Compare results to established laboratory standards and published literature values for similar sample types.
Document processing parameters including buffer lot numbers, incubation times, and environmental conditions for each sample to enable troubleshooting and protocol refinement. Maintain detailed records of any protocol deviations and their impact on final results for continuous improvement purposes. Prepare data for inclusion in research publications following established guidelines for cell preparation methodology reporting.
Quality Control Measures
Implement systematic quality control procedures including buffer pH verification before each use and regular calibration of cell counting equipment. Process control samples with each batch to verify consistent performance and identify potential reagent or equipment issues. Maintain detailed logs of all reagent preparation including lot numbers, preparation dates, and storage conditions for traceability purposes.
Establish acceptance criteria for cell recovery (>70%), viability (>90%), and purity (<5% RBC contamination) with clear procedures for handling samples not meeting specifications. Conduct regular inter-operator comparisons to ensure consistent technique across laboratory personnel. Document all quality control activities and corrective actions taken when results fall outside acceptable ranges.
Key Takeaways
- Red blood cell lysis provides essential sample preparation for flow cytometry and immunophenotyping by removing interfering erythrocyte populations while preserving nucleated cells.
- Proper timing and buffer conditions prevent over-lysis damage while ensuring complete RBC removal, maintaining >90% cell viability for downstream applications.
- Experts recommend this technique as fundamental for hematopoietic research, immune system studies, and cellular therapy development in rodent models.
Related Articles
- Flow Cytometry Sample Preparation Protocol – Comprehensive guide for preparing cellular samples for multiparameter flow cytometric analysis including antibody staining procedures.
- Bone Marrow Cell Isolation from Rodents – Detailed methodology for harvesting and processing bone marrow cells for hematopoietic research applications.
