Non-Toxic Calcein AM Release Assay for Direct NK Cell Killing
Typical NK cell-mediated killing involves accessory signaling or interactions in order to induce NK cell activation and downstream cytotoxicity. NK-cells can be activated by antigen presenting cells and/or multiple cytokines.
To examine direct NK cell-killing, there are two methods. One, the purified NK cells are genetically engineered to identify, bind to and kill target tumor cells. Two, human PBMCs containing NK cells are further stimulated with IL-2 to induce a more robust activation and promote target cell killing.
Traditionally, cytotoxicity assays have been performed using Chromium-51 release, LDH release, Luciferase Reporter Assay and fluorescent release assays (described below).
Alternatively, by labeling the target tumor cells with non-toxic, non-radioactive calcein AM, we can monitor the killing of the tumor cells by the immune effector cells by performing a calcein AM release assay.