Natural Killer (NK) cells perform various activities related to the killing of virally infected cells or cancer cells. NK cells contain secretory lysosomes, i.e. vesicles containing Perforin and granzymes. When NK cells sense a transformed cell, the NK cells attempt to kill this cell (target cell). The NK cells release the contents of the lysosomes, leading to the induction of target cell death by apoptosis. Perforin creates holes in the target cell membrane, and the granzymes move into the target cell to initiate the apoptotic process via the induction of caspases.
Therefore, a measure of NK cell activity requires the presence of potential transformed target cells, and the measurement of activity may include:
- Measurement of target cell death by staining for viability/apoptosis, evaluated by flow cytometry
- Measurement of secreted Perforin and granzymes, using the Luminex platform
- Measurement of CD107a on the NK cell surface, transiently expressed during release of lysosome content, using flow cytometry.
We recommend that the testing of NK cell activation be performed before this more detailed evaluation of NK cell activities is considered.