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Multiple mechanisms of target cell disintegration are employed in cytotoxicity reactions mediated by human natural
C L Sevilla1, G Radcliff, N H Mahle
1Department of Chemistry, Oakland University, Rochester, Mich.
Abstract:
The rate of disintegration of target cells subsequent to lytic programming by human peripheral blood natural killer (NK) cells was investigated using a quantitative calcium pulse technique. The rate of this initial calcium-independent target cell disintegration was indicative of a first-order decay process for programmed target cells with a calculated half-life of less than 3 min. This initial, rapid disintegration phase was independent of the overall cytotoxic activity of the lymphocyte preparation tested. Moreover, initial rates of target cell disintegration were comparable for target cell lines that exhibit up to 6-fold differences in overall susceptibility to natural cytotoxicity. In these studies we also consistently observed very slow, calcium-independent disintegration of additional target cells following apparent completion of the rapid disintegration process. Using a 51Cr release assay and K-562 target cells, the kinetics of this slow disintegration process were examined and found to be similar for donors exhibiting up to a 2-fold difference in overall cytotoxic activity and independent of the concentration of programed target cells. Whereas the initial rapid disintegration mechanism was independent of temperature over the range of 10-37 degrees C, the slow disintegration mechanism exhibited a direct dependence on the incubation temperature. Furthermore, we observed that supernatants obtained after the termination of lytic programing by ethylene diaminetetraacetic acid could effect the slow lysis of fresh NK-susceptible target cell lines. These results support the utilization of at least two distinct mechanisms for target cell lysis by human NK cells.
Insights
Human natural killer (NK) cells employ at least two distinct mechanisms for target cell lysis. These involve a rapid, calcium-independent disintegration and a slower, temperature-dependent lysis, indicating complex cytotoxic pathways.
Area of Science:
- Immunology
- Cell Biology
Background:
- Natural killer (NK) cells are crucial for innate immunity, mediating target cell lysis.
- Understanding the precise mechanisms of NK cell-mediated cytotoxicity is essential for immunology research.
Purpose of the Study:
- To investigate the kinetics and mechanisms of target cell disintegration induced by human peripheral blood NK cells.
- To determine if NK cell lysis involves single or multiple distinct processes.
Main Methods:
- Quantitative calcium pulse technique to measure target cell disintegration rates.
- 51Cr release assay using K-562 target cells to examine lysis kinetics.
- Varied incubation temperatures and ethylene diaminetetraacetic acid treatments to differentiate lysis mechanisms.
Main Results:
- Identified an initial, rapid, calcium-independent target cell disintegration with a half-life under 3 minutes.
- Observed a secondary, slow, calcium-independent target cell disintegration that is temperature-dependent.
- Demonstrated that lysis supernatants could induce slow lysis, suggesting soluble factors are involved.
- Found both rapid and slow lysis phases were largely independent of NK cell donor cytotoxic activity variations.
Conclusions:
- Human NK cells utilize at least two distinct mechanisms for target cell lysis.
- The rapid phase is a calcium-independent process, while the slow phase is temperature-dependent and potentially involves secreted factors.
- These findings elucidate the complexity of NK cell cytotoxic pathways.