Some of your body's cells have a 'license to kill'

Millions of "natural killer cells" -- nature's first line of defense against cancer, viruses and other infectious microbes --- are on constant patrol inside your body.

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<p><a href="http://www.physorg.com/news154541184.html">Some of your body's cells have a 'license to kill'</a></p> <p>Millions of "natural killer cells" -- nature's first line of defense against cancer, viruses and other infectious microbes --- are on constant patrol inside your body.</p>