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Updated: Aug 10, 2026
A Flow Cytometry-Based Cytotoxicity Assay for the Assessment of Human NK Cell Activity
Published on: August 9, 2017
An inducer of NKCF (NK cytotoxic factor) release: localization on target-cell membrane and initial characterization
Z Reiter1, A Loyter, O Nussbaum
1Department of Molecular Genetics and Virology, Weizmann Institute of Science, Rehovot, Israel.
Abstract:
Natural killer (NK) cells are probably involved in the elimination of virus-infected cells and of certain tumor cells. NK cell-mediated cytotoxicity (NK-CMC) was extensively studied and was found to consist of several steps. Following recognition and conjugation between the effector and the target cell, the latter one induces release of NK cytotoxic factor (NKCF) from the effector cells. The NKCF binds to the target cell which is subsequently killed. None of the molecules involved in these steps was completely characterized. In the present study it is demonstrated that isolated membranes of target cells can effectively induce the release of NKCF. Furthermore, the activity of such isolated membranes was found to be modulated by interferon (IFN) treatment of the cells prior to membrane isolation. It was therefore concluded that an NKCF-inducing structure (NKIS) is present on plasma membranes and is distinct from the NK-recognition structure. Similarly, the sensitivity to NK-CMC could be transferred from sensitive cells to IFN-gamma-treated (NK-resistant) cells by membrane fusion with the aid of Sendai virus envelope glycoproteins. It is proposed that transfer of NKIS is responsible for the acquired sensitivity to NK-CMC. In addition, it is shown that NKIS activity was recovered following membrane solubilization and reconstitution. Its level on cell surface was modulated by treatment of cells with tunicamycin, thus indicating that NKIS was probably a cell surface glycoprotein.
Insights
Natural killer cell-mediated cytotoxicity involves a specific NKCF-inducing structure (NKIS) on target cell membranes. Interferon treatment and membrane transfer studies reveal NKIS
Area of Science:
- Immunology
- Cell Biology
Background:
- Natural killer (NK) cells eliminate virus-infected and tumor cells via NK cell-mediated cytotoxicity (NK-CMC).
- NK-CMC involves sequential steps: recognition, conjugation, NK cytotoxic factor (NKCF) release, NKCF binding, and target cell lysis.
- Key molecules mediating NK-CMC remain incompletely characterized.
Purpose of the Study:
- To identify and characterize the molecules involved in NK cell recognition and target cell killing.
- To investigate the role of cell surface structures in NK cell-mediated cytotoxicity.
- To explore the modulation of NK-CMC by interferon (IFN) and tunicamycin.
Main Methods:
- Isolation and use of target cell membranes to induce NKCF release.
- Membrane fusion experiments using Sendai virus envelope glycoproteins to transfer sensitivity.
- Solubilization and reconstitution of membrane components.
- Modulation of cell surface structures with tunicamycin.
Main Results:
- Isolated target cell membranes induced NKCF release, suggesting the presence of an NKCF-inducing structure (NKIS).
- Interferon (IFN) treatment modulated the activity of isolated membranes.
- Sensitivity to NK-CMC was transferable to NK-resistant cells via membrane fusion, indicating transfer of NKIS.
- NKIS activity was recovered after solubilization and reconstitution, and its surface level was modulated by tunicamycin, suggesting it is a glycoprotein.
Conclusions:
- An NKCF-inducing structure (NKIS), distinct from the NK-recognition structure, resides on plasma membranes.
- NKIS transfer mediates acquired sensitivity to NK-CMC.
- NKIS is likely a cell surface glycoprotein whose expression is regulated.
