As the basic mechanism that allows our bodies to identify, target, and kill infected or damaged cells, cell-mediated cytotoxicity is an essential function of our immune system and one that scientists continue to explore to develop more advanced immunotherapies.
By better understanding the role of T cells and natural killer cells as effector cells and different measurement methods, researchers can more accurately study the functions of these important immune cells in vitro.
An 8-Minute Read
Take a few minutes to read this white paper for an overview of the types of cell-mediated cytotoxicity and various measurement methods. You will learn about:
- Antigen-Specific Cell-Mediated Cytotoxicity
- Antibody-Dependent Cellular Cytotoxicity
- Natural Killer Cell-Mediated Cytotoxicity
- Chromium-51 (51Cr) Release
- Lactate Dehydrogenase (LDH) Release
- Calcein Release
- Staining to Detect Degranulation
- Flow Cytometry
Measuring Cell-Mediated Cytotoxicity
1. Antigen-Specific T Cell-Mediated Cytotoxicity
Antigen-specific T cell receptors bind to MHC class I molecules; CD8+ T cells release perforin and granzymes
Employed by cancer immunotherapies targeting immune checkpoints
2. Antibody-Dependent Cellular Cytotoxicity
Fc receptors on effector cells bind to antibodies on the surface of target cells; effector cells release cytotoxic granzymes
Utilized by certain antibody-based drugs, such as Herceptin® and Rituxan®
3. Natural Killer Cell-Mediated Cytotoxicity
Requires neither antibody nor antigen expression; NK cells directly recognize target cells and release cytokines
Chimeric antigen receptors (CARs) engineered into NK cells as alternative
Measurement Methods
1. Chromium-51 Release
Target cells are labeled with 51Cr and release 51Cr through cell lysis.
- Sensitive — the release of 51Cr is easy to detect
- Measures death of target cells, not death of killer cells
- Some leakage of the label, higher background
- Requires hazardous materials
2. Lactate Dehydrogenase (LDH) Release
Measures amount of soluble cytosolic enzyme released during cell death using colorimetric readout.
- LDH is more stable than other enzymes
- No label required
- Release of LDH is not limited to the target cells
- High background
3. Calcein Release
Target cells are labeled with highly fluorescent Calcein AM. Damaged and killed cells release Calcein into culture.
- Can be detected using fluorescent plate reader
- Label is specific to target cells
- High background
4. Staining to Detect Degranulation
Directly labeled anti-CD107a added to T cells or NK cells prior to exposure to target cells. Allows for detection of antigen during degranulation.
- Only requires one label
- Low background
- May miss degranulation
- Flow cytometer needed
5. Flow Cytometry
Target cells are labeled with a fluorescent viability dye to differentiate them from the effector cells.
- Deeper analysis
- High sensitivity
- Not as easily read in larger assays
