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Mechanism of cell contact-mediated inhibition of natural killer activity
Abstract:
Natural killer cell activity is inhibited by primary cultures of monolayer cells. In this study, we analyzed the mechanism of the inhibition. Inhibited NK cells showed unaltered binding capacity to NK sensitive K562 cells. The orientation of the effector cells' actin-containing microfilaments, an event known to occur during the programming for the lysis stage in lytic conjugates, was unaffected by the inhibition. In single cell cytotoxicity experiments, the number of killer cells among conjugate-forming cells was reduced. The capacity of the inactivated NK cells to secrete cytotoxic factors upon stimulation with Con A was also impaired. Both NK-resistant inactivating target cells and NK-sensitive K562 cells were sensitive to the toxic factors secreted by NK cells. Thus, the results indicate that the target cell-mediated inactivation of NK cell is based on a block in the lethal hit stage, possibly due to reduced release of toxic factor(s) from the effector cells. The capacity of inactivated effector cells to mediate antibody-dependent cellular cytotoxicity was unimpaired, suggesting that the contact-mediated inhibition of cytotoxicity selectively affects NK cells.
Insights
Primary cells can inhibit natural killer (NK) cell activity by blocking the lethal hit stage. This impairment stems from reduced cytotoxic factor release, selectively affecting NK cell function.
Area of Science:
- Immunology
- Cell Biology
Background:
- Natural killer (NK) cells are crucial for innate immunity.
- NK cell activity can be modulated by other cell types.
Purpose of the Study:
- To elucidate the mechanism by which primary monolayer cells inhibit NK cell activity.
- To determine the specific stage of NK cell function affected by this inhibition.
Main Methods:
- Analysis of NK cell binding and conjugate formation with target cells.
- Assessment of actin microfilament organization in effector cells.
- Single-cell cytotoxicity assays.
- Evaluation of cytotoxic factor secretion and antibody-dependent cellular cytotoxicity (ADCC).
Main Results:
- Inhibited NK cells maintained binding capacity but showed reduced conjugate formation with target cells.
- Actin microfilament orientation, crucial for lysis programming, remained unaffected.
- NK cell secretion of cytotoxic factors was impaired, while ADCC remained intact.
- Both NK-sensitive and NK-resistant cells were susceptible to NK cell cytotoxic factors.
Conclusions:
- Target cell-mediated inactivation of NK cells involves a block in the lethal hit stage.
- This inhibition is likely due to impaired release of cytotoxic factors from effector NK cells.
- The observed inhibition selectively impacts NK cell-mediated cytotoxicity, sparing ADCC.