DELFIA time-resolved fluorescence cell cytotoxicity assays offer a non-radioactive method to Chromium 51, for use in cell-mediated cytotoxicity and antibody-dependent cell cytotoxicity (ADCC) studies. The method is based on loading cells with an acetoxymethyl ester of a fluorescence enhancing ligand. After the ligand has penetrated the cell membrane the ester bonds are hydrolyzed within the cell to form a hydrophilic ligand, which no longer passes through the membrane. After cytolysis the released ligand is introduced to a europium solution to form a fluorescent chelate. The measured signal correlates directly with the amount of lysed cells.

Reagents for the assay are also available separately:

• Lysis buffer (30 mL), #4005-0010
• DELFIA Eu-Solution (200 mL), #C135-100
• DELFIA BATDA labeling reagent (50 µL), #C136-100

Selected references:

1. Lazar, G. A. et al. Engineered antibody Fc variants with enhanced effector function. PNAS 103, 4005-4010 (2006).
2. Tsai, C.-Y. et al. Type I IFNs and IL-18 Regulate the Antiviral Response of Primary Human γδ T Cells against Dendritic Cells Infected with Dengue Virus. The Journal of Immunology 194, 3890-3900 (2015).
3. Mehta, R. S., Chen, X., Antony, J., Boyiadzis, M. & Szabolcs, P. Generating Peripheral Blood Derived Lymphocytes Reacting Against Autologous Primary AML Blasts. J Immunother 39, 71-80 (2016).
4. Snyder, K. M. et al. Expression of a Recombinant High Affinity IgG Fc Receptor by Engineered NK Cells as a Docking Platform for Therapeutic mAbs to Target Cancer Cells. Front Immunol 9, (2018).
5. Yu, T., Qiao, C., Lv, M. & Tang, L. Novel anti-CD38 humanized mAb SG003 possessed enhanced cytotoxicity in lymphoma than Daratumumab via antibody-dependent cell-mediated cytotoxicity. BMC Biotechnology 19, 28 (2019).