Poison Pellet
Caught in the act
A high-powered microscope image reveals that molecule filaments (blue) move aside to guide an immune cell's poison pill (yellow) out where it can kill the enemy
Microscopic images of disease-fighting cells may one day help treat immune deficiency disorders. Jordan Orange of the Children's Hospital of Philadelphia and colleagues used a superpowerful new microscope to watch how immune cells called natural killer cells feed a poison pill called a lytic granule to tumors or virus-infected cells. Scientists used to think a big hole in the middle of a dense mesh of spaghetti-like molecules called F-actin let granules stream out of the natural killer cell. But the new study, published online September 13 in PLoS Biology, shows that the meshwork parts just enough to let single lytic granules pass, with F-actin helping squeeze the granule through. People with immune deficiency disorders may have defects that prevent lytic granules from exiting the natural killer cell. The H5N1 avian influenza virus may get its killing power from its host. It hasn't been clear whether humans die from having lots of viruses in their lungs or from making too many inflammation-producing chemicals. Now researchers at St. Jude Children's Research Hospital in Memphis, Tenn., and Roche Pharmaceuticals in Palo Alto, Calif., have evidence from studies in mice that the victim's own genetic makeup determines how well the virus grows in the lungs. Genetically susceptible mouse strains had more viruses in their lungs than resistant strains, the team reports online September 6 in mBio.
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