Quick answer
Immune cell isolation depends on gentle mechanical processing, clean suspension, and fit-for-purpose enrichment
Mouse spleen and lymph nodes are common sources of primary immune cells for immunology research. These tissues contain lymphocytes and other immune populations that can be isolated for flow cytometry, cell culture, activation studies, cytokine assays, proliferation experiments, or functional testing.
Unlike many dense solid tissues, spleen and lymph nodes can often be dissociated primarily through gentle mechanical disruption. The major objectives are to obtain a clean single-cell suspension, preserve cell viability, and minimize unnecessary activation of the immune cells.
Protocol boundary
Use this as general guidance
Cell-line-specific instructions, supplier recovery notes, institutional biosafety requirements, and your lab's validated SOP should take priority when they differ from this general workflow.
Workflow step
Step 1: Harvest Spleen and Lymph Nodes
Collect the spleen and required lymph nodes according to approved animal procedures.
Place tissues promptly into chilled physiological buffer or appropriate complete medium.
Common lymph nodes used for immune-cell isolation include inguinal, axillary, mesenteric, and cervical nodes, depending on the experimental question.
Remove obvious adipose and connective tissue before processing.
Keep tissues appropriately chilled during preparation unless the validated assay requires different handling. Excessive delays can reduce viability and alter immune-cell responses.
Workflow step
Step 2: Prepare Single-Cell Suspension
Place the spleen or lymph nodes into a sterile dish containing buffer or medium.
Gently disrupt the tissue mechanically using an appropriate sterile method. The goal is to release cells without excessive grinding that could rupture cells and generate debris.
Pass the resulting suspension through a 70 µm cell strainer to remove connective tissue, tissue fragments, and large aggregates.
Rinse the strainer with additional buffer to recover remaining cells.
Gentle mechanical processing is usually sufficient for routine lymphocyte isolation from lymph nodes and spleen. More complex immune populations, particularly stromal or myeloid populations embedded within tissue architecture, may require additional enzymatic digestion.
After filtration, centrifuge and resuspend the cells according to the intended downstream workflow.
Workflow step
Step 3: Remove Red Blood Cells
The mouse spleen contains a substantial red blood cell population, making erythrocyte removal an important step for many assays.
Treat splenic cell suspensions briefly with ACK red blood cell lysis buffer according to the validated laboratory procedure.
ACK-based lysis preferentially disrupts erythrocytes while preserving most nucleated immune cells when exposure is properly controlled.
Do not extend lysis longer than necessary. Excessive exposure can reduce lymphocyte viability.
Stop the lysis by adding sufficient physiological buffer or complete medium, then centrifuge and remove the supernatant.
Lymph node preparations generally contain far fewer red blood cells and may not require routine RBC lysis unless visible erythrocyte contamination is present.
Count viable nucleated cells before proceeding.
Workflow step
Step 4: Enrich Specific Immune Cell Populations (Optional)
The resulting single-cell suspension contains multiple immune-cell populations.
For many flow cytometry experiments, enrichment is unnecessary because cell subsets can be identified directly using antibody panels.
When purified populations are required, additional enrichment can be performed.
Magnetic Enrichment
Magnetic bead-based selection can enrich or deplete populations such as:
T cells
B cells
CD4⁺ T cells
CD8⁺ T cells
Monocytes or macrophages
Dendritic-cell populations
Positive selection captures the desired cells directly, while negative selection removes unwanted populations and leaves the target population relatively untouched.
Density-Gradient Separation
Density gradients can be used in selected workflows to separate viable mononuclear cells from debris or other cellular components.
The appropriate method depends on required purity, cell number, activation sensitivity, and downstream experiment.
After enrichment, reassess cell concentration and viability before culture or functional assays.
Expected Results
Expected Results
A successful spleen preparation should produce a high-density single-cell suspension with limited visible tissue debris after filtration and RBC lysis.
Lymph node preparations generally produce fewer total cells but should contain relatively clean lymphocyte-rich suspensions.
Healthy lymphocytes are small, round cells. Viability should remain high when tissues are processed promptly and gently.
For downstream flow cytometry, the sample should contain relatively few aggregates to reduce acquisition problems and doublets.
Troubleshooting
Common problems to check
Low Cell Yield
Incomplete mechanical disruption or cell loss during filtration can reduce recovery. Ensure the tissue is thoroughly but gently dissociated.
Excessive Red Blood Cells
Confirm that ACK lysis was performed effectively. A second brief treatment may occasionally be required, but repeated exposure can reduce immune-cell viability.
Cell Clumping
Cell damage and released DNA can promote aggregation. Avoid aggressive tissue crushing and excessive handling.
Low Viability
Delayed processing, prolonged RBC lysis, harsh mechanical disruption, or inappropriate temperature conditions may contribute.
FAQ
Common questions
Do lymph nodes require ACK lysis?
Usually not unless substantial red blood cell contamination is present.
Why use a 70 µm strainer?
It removes large tissue fragments and aggregates while allowing most individual immune cells to pass through.
Do I need to enrich T or B cells before flow cytometry?
Not necessarily. Enrichment is mainly needed when the downstream experiment requires a purified population or when the target population is rare.
Can isolated cells be cultured immediately?
Yes, provided appropriate medium and stimulation conditions are used for the intended immune-cell population.
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