Related Experiment Videos
Cytolytic lymphocytes induce both apoptosis and necrosis in target cells
A Zychlinsky1, L M Zheng, C C Liu
1Laboratory of Cellular Physiology and Immunology, Rockefeller University, New York, NY 10021.
Abstract:
We examined the role of programmed cell death (apoptosis) in killer lymphocyte-mediated cytotoxicity. Two parameters of cell death, 51Cr release and DNA fragmentation, were assayed. Lymphokine-activated killer cell- or CTL-mediated death was inhibited in target cells where transcription or translation were blocked. Dying target cells showed ultrastructural changes typically associated with both apoptosis and necrosis. In contrast, target cells pretreated with macromolecular synthesis inhibitors and incubated with lymphokine-activated killer cells showed morphologic signs of necrosis only. Zn2+, an inhibitor of endonucleases, inhibited DNA fragmentation, but not 51Cr release in YAC-1 target cells, suggesting that the two effects can be dissociated. Finally, the cytotoxic effect of perforin, a pore-forming protein of killer lymphocytes that is known to cause necrotic death, was unaffected by the inhibition of either RNA or protein synthesis in target cells. Taken together, these results suggest that killer lymphocytes can induce both necrosis and apoptosis and that the two types of death can be dissociated with specific inhibitors.
Insights
Killer lymphocytes induce both apoptosis and necrosis in target cells. Specific inhibitors can dissociate these programmed cell death pathways, revealing distinct mechanisms in cytotoxicity.
Area of Science:
- Immunology
- Cell Biology
Background:
- Killer lymphocytes play a crucial role in immune surveillance and elimination of target cells.
- Programmed cell death, including apoptosis and necrosis, are key mechanisms in cellular regulation and elimination.
Purpose of the Study:
- To investigate the distinct roles and mechanisms of apoptosis and necrosis induced by killer lymphocytes.
- To determine if killer lymphocyte-mediated cell death pathways can be pharmacologically dissociated.
Main Methods:
- Assaying 51Cr release and DNA fragmentation as markers of cell death.
- Utilizing macromolecular synthesis inhibitors and endonuclease inhibitors (Zn2+) in target cells.
- Examining ultrastructural changes in dying target cells via microscopy.
- Assessing the cytotoxic effects of perforin, a key killer lymphocyte protein.
Main Results:
- Killer lymphocyte-mediated cell death was inhibited by blocking transcription or translation in target cells.
- Dying target cells exhibited ultrastructural features of both apoptosis and necrosis.
- Inhibition of DNA fragmentation by Zn2+ did not prevent 51Cr release, dissociating these death parameters.
- Perforin-mediated cytotoxicity was independent of target cell RNA or protein synthesis.
Conclusions:
- Killer lymphocytes can induce both apoptotic and necrotic cell death.
- Apoptosis and necrosis induced by killer lymphocytes represent distinct, dissociable processes.
- Target cell macromolecular synthesis is involved in apoptosis but not necessarily necrosis during killer cell interactions.