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May 2012

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Standard 4-hours Chromium-51 (51Cr) Release Assay    

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51Cr-release assays are commonly used for the precise and accurate quantification of cytotoxicity, particularly in the study of tumor cytolysis. This test has the advantage of requiring only very few cells.

Materials and Reagents

  1. Target cells: Acute Myeloid Leukemia (AML) cell line (U937 or HL60 from ATCC) or AML cells isolated from patients with AML
  2. Effector cells: γδ T cells isolated from Healthy volunteer provided by Etablissement
  3. Francais du Sang (EFS) or patients
  4. Medium : RPMI 1640 (Life Technologies, Gibco®)
  5. Fetal Calf Serum (FCS) heat-inactivated 1 h at 56 °C
  6. Chromium-51 (51Cr, 5 mCi/ml) (PerkinElmer)
  7. Complete medium = RPMI 1640 medium supplemented with 10% heat-inactivated FCS


  1. Centrifuge for microplates
  2. Microplates (96 well round-bottom) for cell incubations
  3. LumaPlateTM (PerkinElmer)
  4. Liquid scintillation counter
  5. Incubator


  1. Spontaneous Release: Target cells were incubated alone (replace effector cells by 50 μl of media). After 4 h of incubation, wells were centrifuged and 50 μl of supernatant were recovered.
  2. Maximum load: Target cells were incubated alone (replace effector cells by 50 μl of media). After 4 h of incubation, wells were mixed and 50 μl of cell suspension were recovered rather than disrupt the cell membrane to release the radioactivity into the supernatant). This avoids the use of detergent.


  1. 51Cr labeling the target cells
    1. Wash targets (2.106 per condition) in 15 ml of medium.
    2. Centrifuge targets; discard the supernatant and resuspend pellets in 20 μl of FCS.
    3. Add 100 μCi of 51Cr (20 μl of stock solution at 5 mCi/ml) for one hour in an incubator at 37 °C.
      NB: To define the dose of chromium necessary to mark a cell type, it must be ensured that the spontaneous release is less than 10% of maximum load.
    4. Wash cells and resuspend in 60,000 cells per ml of complete medium.
    5. Add 3,000 Target cells per well in 50 μl of a round-bottom 96 well plate.

  2. Incubation of target cells with effector cells
    1. Add effector cells (50 μl) at E:T (Effetor:Target) ratios of 30:1, 20:1, 10:1, and 1:1. In parallel, set up controls (Spontaneous Release, Maximum load) and incubate 4 h at 37 °C.

  3. Analysis
    1. Centrifuge samples and collect supernatant (50 μl).
    2. Supernatants are dried on a LumaPlateTM (PerkinElmer) overnight and counted in a liquid scintillation counter.
      The percentage of specific lysis was calculated using the standard formula [(experimental - spontaneous release)/(maximum load- spontaneous release) x 100] and expressed as the mean of triplicate samples


This protocol is adapted from Gertner-Dardenne et al. (2012).


  1. Gertner-Dardenne, J., Castellano, R., Mamessier, E., Garbit, S., Kochbati, E., Etienne, A., Charbonnier, A., Collette, Y., Vey, N. and Olive, D. (2012). Human Vgamma9Vdelta2 T cells specifically recognize and kill acute myeloid leukemic blasts. J Immunol 188(9): 4701-4708.
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Copyright: © 2012 The Authors; exclusive licensee Bio-protocol LLC.
How to cite: Gertner-dardenne, J. (2012). Standard 4-hours Chromium-51 (51Cr) Release Assay. Bio-protocol 2(23): e301. DOI: 10.21769/BioProtoc.301.

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