NK-92 Cell Line Culture Protocol

Dillon Corvino

Culture and maintenance of the human NK-92 cell line, including thawing, IL-2–supplemented culture, routine passaging, and cryopreservation.
Published

November 21, 2025

Protocol ID: HUM-NK92-CULTURE
Version: v1.1
Author: Dillon Corvino

Purpose

This protocol describes thawing, routine culture, IL-2–supplemented maintenance, passaging, and cryopreservation of the human NK-92 cell line. NK-92 is a suspension NK-like cell line requiring continuous IL-2 supplementation for viability, proliferation, and maintenance of cytotoxic phenotype.

Critical notes (read before starting)

  • NK-92 is a human clinical-grade NK cell line and must be handled under strict BSL2 conditions.
  • NK-92 requires continuous IL-2 supplementation for survival. Never culture NK-92 in IL-2–free medium.
  • NK-92 is typically cultured at 200–500 IU/mL IL-2 (lab-validated range should be consistent).
  • NK-92 grows in suspension but forms loose aggregates; avoid over-pipetting or harsh centrifugation.
  • Passage NK-92 before cultures become dense or acidic; overgrown cultures lose cytotoxicity and viability.
  • Cryopreserved NK-92 must be thawed quickly and washed immediately to remove DMSO.
Warning

NK-92 viability rapidly decreases if IL-2 is omitted or if medium becomes depleted. Always add IL-2 fresh to pre-warmed medium before feeding or splitting.

Tip

For reproducibility, record IL-2 batch number, concentration added, split ratio, and passage number at every passage.

Approximate timing

  • Thawing: 15–20 min
  • Routine maintenance and splitting: 10–20 min
  • Cryopreservation: 20–30 min
  • Hands-on time per culture session: ~15–30 min

Procedure

Step 1 – Medium and reagent preparation

  1. Prepare complete NK-92 medium:
    • RPMI 1640
    • 10% heat-inactivated FCS
    • 1% Pen/Strep
  2. Prepare IL-2 working aliquots.
  3. Supplement complete medium with IL-2 immediately before use:
    • 200 IU/mL final (or your lab-validated concentration).
  4. Pre-warm:
    • NK-92 complete medium + IL-2
    • PBS (if washing is needed)
      to 37 °C.
Note

IL-2 is unstable when stored in complete medium. Always add fresh, immediately before feeding.

Step 2 – Thawing NK-92 cells

  1. Remove a cryovial from liquid nitrogen and place immediately in a 37 °C water bath.
  2. Gently swirl until only a small ice crystal remains.
  3. Disinfect the vial and transfer to a biosafety cabinet.
  4. Transfer the contents to a 15 mL tube containing 9–10 mL pre-warmed medium without IL-2 to dilute DMSO.
  5. Centrifuge at 300 g for 5 min.
  6. Carefully aspirate supernatant.
  7. Gently resuspend the pellet in 10–15 mL NK-92 complete medium with IL-2.
  8. Transfer cells to a T25 or T75 flask and incubate at 37 °C, 5% CO₂.
Warning

Do not expose thawed cells to DMSO for more than a few minutes; wash immediately after thawing.

Step 3 – Routine culture and passaging

Procedure

  1. Gently pipette or swirl flask to resuspend cells uniformly.
  2. Remove an aliquot for counting and viability.
  3. If density exceeds 1 × 10⁶ cells/mL, split culture:
    • Remove part of the culture (e.g., ½–¾ volume).
    • Replace with fresh NK-92 medium + IL-2.
  4. Restore cultures to 2–3 × 10⁵ cells/mL.
  5. Return flasks to incubator.

Full medium change for stressed cultures

  1. Collect cells and centrifuge at 300 g for 5 min.
  2. Aspirate depleted medium.
  3. Resuspend cells in fresh complete NK-92 medium + IL-2.
Note

Fresh IL-2 medium is essential after any decline in viability; NK-92 responds rapidly to improved culture conditions.

Step 4 – Preparing NK-92 cells for experiments

  1. For functional assays, activate cultures 24 hours before experiments using:
    • Fresh NK-92 complete medium + IL-2
  2. Seed cultures at defined densities (e.g., 2–3 × 10⁵ cells/mL).
  3. Avoid using NK-92 beyond a set passage number (e.g., <20 passages post-thaw).

Step 5 – Cryopreservation of NK-92 cells

Freezing medium

  • 90% FCS + 10% DMSO, or
  • Mix cell suspension 1:1 with BUF-FREEZE-MIX for a final 10% DMSO freezing medium.

Procedure

  1. Harvest NK-92 cells during exponential growth.
  2. Centrifuge at 300 g for 5 min.
  3. Resuspend cells at 5–10 × 10⁶ cells/mL in freezing medium.
  4. Aliquot 1 mL per labelled cryovial.
  5. Place into a controlled-rate freezing container (Mr Frosty).
  6. Freeze at −70/−80 °C for ≥12 hours.
  7. Transfer to liquid nitrogen for long-term storage.

Buffers Required

Full composition, preparation, storage, and safety information for each buffer lives in its own linked buffer document — only a concise per-buffer summary is reproduced here, generated automatically from that document.

2x Freezing Medium

Component Final concentration / amount
RPMI 1640 (R0) base medium (7 mL per 10 mL batch)
Fetal calf serum 10% (v/v)
DMSO (cell-grade) 20% (v/v)
  • Final volume: 10 mL (2x concentrate; example batch, scale as needed)
  • Preparation note: Mix gently by inversion; do not vortex. Keep on ice until use.
  • Storage: Use fresh on day of preparation; do not store; discard any unused buffer.
  • Caveat: DMSO is toxic at room temperature - keep the 2x mix on ice and mix with cells immediately after preparation. Final working freezing medium (after 1:1 mix with cells) contains 10% DMSO.

Full composition, preparation steps, storage, and safety information: BUF-FREEZE-MIX.

Materials

Reagents

Reagent Supplier Cat. # Notes
RPMI 1640 Various — Base medium
Fetal calf serum (FCS) Various — 10% in culture, 90% in freezing medium
Penicillin/Streptomycin Various — 1% final in medium
Recombinant human IL-2 PeproTech/etc. — 200 IU/mL final
DMSO, cell-grade Sigma/etc. — 10% final for freezing
PBS, 1× Various — For optional washes

Disposables

Item Specification
T25 / T75 flasks Vent-cap, sterile
15 mL / 50 mL tubes Sterile
Cryovials LN₂ compatible
Serological pipettes Sterile (5–25 mL)
Pipette tips Sterile (10–1000 µL)

Equipment

Equipment Specification / Notes
CO₂ incubator 37 °C, 5% CO₂
Biological safety cabinet BSL2 work
Benchtop centrifuge 300 g for washing
Water bath 37 °C for thawing
Controlled-rate freezer e.g., Mr Frosty
−70/−80 °C freezer For initial freezing
Liquid nitrogen storage Long-term storage
Cell counter/hemocytometer For counting

Troubleshooting

Issue Possible cause Suggested solution
Poor viability after thaw Slow thawing; prolonged DMSO exposure Thaw rapidly; wash promptly; ensure gentle handling
Slow growth Insufficient IL-2; old medium Increase IL-2 (within validated range); refresh medium
Excessive clumping Overgrowth or nutrient depletion Split earlier; replace medium entirely
Reduced cytotoxicity High passage number; inconsistent IL-2 Use low-passage cells; standardise IL-2 concentration
Contamination Aseptic technique failure Discard culture and restart from frozen stock

Safety (brief)

  • NK-92 is a human-derived cell line and must be handled under BSL2.
  • Wear gloves, lab coat, and eye protection.
  • Dispose of all culture waste as biohazardous.
  • Handle DMSO cautiously; it increases dermal absorption of contaminants.
  • Follow institutional protocols for cryogen handling and LN₂ storage.

Version history

Version Date Author Changes
v1.0 2025-11-21 Dillon Corvino Initial Quarto protocol for NK-92 culture
v1.1 2026-09-18 Dillon Corvino Replaced # Buffers used (bare library(tidyverse), leaked R package-startup warnings) with an auto-generated # Buffers Required section; moved it from after Materials to before Materials. Fixed stale buffer-ID reference BUF-GEN-FREEZE-MIX-001 -> BUF-FREEZE-MIX in Step 5