Red Blood Cell Lysis Buffer — Technical Description & Operating Guide

1. Background & Objective

Red blood cell (RBC) lysis buffer (ACK) selectively lyses erythrocytes under controlled time and temperature while minimizing damage to nucleated cells, thereby markedly reducing RBC load and preserving cell viability. The goal is to obtain a nucleated-cell suspension with low RBC carryover, high viability, and well-preserved surface antigens, providing consistent input quality for downstream primary culture, flow cytometry, and nucleic-acid/protein extraction.

2. Principle of Action

Ammonium chloride is the key active component. In solution it exists in equilibrium with NH₃/NH₄⁺: NH₃ diffuses across the RBC membrane, while NH₄⁺ exits poorly. Together with the co-influx of Cl⁻, this raises intracellular osmolarity and mildly acidifies the cytosol. Because RBCs lack efficient volume regulation, water influx leads to rapid swelling and hemolysis. Nucleated cells tolerate this short exposure better, enabling selective removal of RBCs.

3. Applications & Storage

•  Separation/purification of single-cell suspensions after enzymatic tissue digestion
• Isolation/purification of lymphocytes from peripheral blood, bone marrow, or spleen
• RBC removal prior to primary culture, cell fusion, or flow cytometry
• Clearing RBCs before protein and nucleic-acid (DNA/RNA) extraction

Storage: 2–8 °C, protected from light. After opening, filter-sterilize through 0.22 µm, aliquot, and keep aseptic (preferably work in a clean bench).

4. Formulation

Preparation:

Dissolve all reagents in ~850 mL deionized water → adjust pH 7.2–7.4 → bring volume to 1,000 mL with water.

5. Instructions for Use

(1) Tissue-derived single-cell suspensions (after enzymatic digestion)

• Prepare single cells: Digest fresh tissue with trypsin/collagenase; disperse to single cells, centrifuge, discard supernatant.
• Add lysis buffer: Add pre-chilled (4 °C) ACK at 1:3–5 (1 mL packed cells : 3–5 mL buffer). Gently pipette to mix.
• Centrifuge & remove supernatant: 800–1000 rpm, 5–8 min; discard red supernatant.
• Wash: Resuspend pellet in Hank’s solution or serum-free medium; wash 2–3× by centrifugation.
• Re-lysis (optional): If RBC removal is insufficient, repeat the add/centrifuge steps once (prefer a brief second treatment over markedly extending a single incubation).
• Resuspend & proceed: Resuspend cells for downstream assays. For RNA extraction, use DEPC-treated buffers/solutions beginning from the wash step.

Note: For samples with antigen-sensitive surfaces, perform the entire RBC-removal procedure at 4 °C; if needed, use short, repeated treatments to improve clearance.

(2) Blood-derived cells (peripheral blood/bone marrow/spleen, anticoagulated)

• Pre-process: Use fresh anticoagulated blood. Centrifuge to remove plasma and discard supernatant.
• Add lysis buffer: Add pre-chilled ACK at 1:6–10 (1 mL packed cells : 6–10 mL buffer). Mix gently.
• Centrifuge & remove supernatant: 800–1000 rpm, 5–8 min; discard red supernatant.
• Wash: Resuspend pellet in  Hank’s solution or serum-free medium; wash 2–3×.
• Re-lysis (optional): Repeat add/centrifuge once if needed.
• Resuspend & proceed: Resuspend for downstream work. For RNA workflows, use DEPC-prepared solutions from the wash step onward.

Timing tips: Mouse blood typically clears in 1–2 min; for human peripheral blood, 4–5 min is recommended, with a 10 min upper limit.

6. Critical Notes & Tips

• Time control: Lysis is time-limited. Prefer short incubations + re-lysis if required; on first use, run a small gradient (1–3 / 3–5 / 5–8 min) to find the window.
• Temperature & mixing: Working at 4 °C reduces metabolism/stress. Mix gently to avoid mechanical damage.
• Wash buffers: Prefer Ca²⁺/Mg²⁺-free PBS/Hank’s solution or serum-free media. For nucleic-acid workflows, maintain a consistent DEPC system.
• Anticoagulants: EDTA is common and flow-compatible; heparin may inhibit some downstream assays (e.g., PCR).
• Sample-to-buffer ratio: Follow the recommended packed-cell : buffer ranges. With high RBC burden, increase buffer volume or slightly extend lysis while monitoring cell status.
• Microscopy checks: At key points (after the first lysis and after the final wash), perform a quick smear/Trypan-blue check to assess RBC removal and viability.
• Contamination control: Keep procedures aseptic. Aliquot after opening to reduce contamination from repeated access.

7. FAQ

Q1: Red coloration remains after lysis.

A: Extend lysis 1–2 min or perform one additional lysis; also check ratio, buffer potency, and contamination.

Q2: Viability of nucleated cells decreases.

A: Likely over-lysis or excessive/long centrifugation. Shorten lysis, reduce g-force/time, and keep at 4 °C.

Q3: High nonspecific background in flow cytometry.

A: Due to residual RBCs/free hemoglobin or insufficient washing. Add an extra wash and ensure buffers are free of RBC carryover.

Q4: Poor RNA yield/integrity.

A: Use a DEPC system from the wash step, minimize room-temperature exposure, and consider RNase inhibitors if necessary.

8. Safety

• Follow BSL-2 practices: gloves, goggles, lab coat.
• Collect liquid/solid waste containing blood/cells as biohazardous chemical waste; dispose according to institutional procedures.
• For spills, promptly treat with 0.5–1% sodium hypochlorite or an equivalent disinfectant.