Medullasin enhances human natural killer cell activity

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Natural killer (NK) cells are crucial for innate immunity.
• Regulation of NK cell activity is vital for immune response.
• Serine proteases play diverse roles in biological processes.

Purpose of the Study:

• To investigate the effect of medullasin on human natural killer cell activity.
• To elucidate the mechanism of medullasin-mediated NK cell activation.
• To determine the source and regulation of medullasin activity.

Main Methods:

• Treatment of human lymphocytes with purified medullasin.
• Assay of natural killer cell cytotoxicity.
• Inhibition studies using protease inhibitors.
• Flow cytometry to assess Fc receptor-bearing lymphocytes.
• Detection of interferon activity.

Main Results:

• Medullasin significantly enhanced NK cell activity following a 37°C incubation period.
• The enhancement was observed at physiological protease concentrations (5-20 µg/ml).
• Medullasin-induced activation was blocked by specific inhibitors and by depleting Fc receptor-bearing lymphocytes.
• Medullasin potentiated interferon-stimulated NK cell activity but did not induce interferon itself.
• Medullasin was released from mature granulocytes and was not detected in unstimulated or mitogen-stimulated lymphocytes.

Conclusions:

• Medullasin is a novel serine protease that activates human natural killer cells.
• NK cell activity regulation involves medullasin released by mature granulocytes.
• Medullasin represents a new target for modulating immune responses.