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In vitro effects of protease inhibitors on murine natural killer cell activity
Abstract:
To test whether proteolytic events are involved in natural killer (NK) cell mediated lysis of tumour cells, twenty-three different protease inhibitors were added to in vitro assays of natural killer cell reactivity. Of all of the materials tested, only tosyl-L-lysine chloromethyl ketone (TLCK), tosyl-L-phenylalanine chloromethyl ketone (TPCK) and benzamidine unequivocally inhibited killing at concentrations approaching those needed to affect appropriate purified proteases. All of the effective inhibitors, and none of the others tested, inhibited binding of effector to target cells. The action of TLCK was focused on both effector and target cells, in that cytolysis was completely inhibited by a 1 hr pretreatment of effectors with 10(-4) M TLCK, and 60% inhibited by a 1 hr treatment of targets only.
Insights
Protease inhibitors like TLCK and TPCK block natural killer (NK) cell killing of tumor cells by preventing immune cell binding. This suggests proteases are crucial for NK cell-mediated tumor cell lysis.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Natural killer (NK) cells are crucial for innate immunity, mediating tumor cell lysis.
- The specific molecular mechanisms, particularly proteolytic events, underlying NK cell cytotoxicity remain incompletely understood.
Purpose of the Study:
- To investigate the role of proteolytic events in NK cell-mediated tumor cell lysis.
- To identify specific protease inhibitors that can block NK cell activity.
Main Methods:
- In vitro assays were performed using NK cells and tumor cells.
- Twenty-three different protease inhibitors were tested for their effect on NK cell reactivity.
- Inhibitor concentrations were compared to those affecting purified proteases.
- Inhibitor effects on effector-target cell binding were assessed.
Main Results:
- Tosyl-L-lysine chloromethyl ketone (TLCK), tosyl-L-phenylalanine chloromethyl ketone (TPCK), and benzamidine were the only inhibitors to significantly inhibit NK cell-mediated killing.
- These effective inhibitors also blocked the binding of NK cells (effectors) to tumor cells (targets).
- TLCK demonstrated inhibitory effects on both effector and target cells.
Conclusions:
- Proteolytic events are involved in NK cell-mediated lysis of tumor cells.
- Specific protease inhibitors, including TLCK and TPCK, can effectively block NK cell cytotoxicity by inhibiting effector-target cell binding.