September 15, 2011

Super Resolution Microscope: Seeing the Immune System

(Ivanhoe Newswire) -- A new tool allows scientists to see the immune system like never before.

The device, a stimulated emission depletion (STED) microscope, provides sharp images at extremely small scales. It shows how granules from natural killer cells pass through openings in dynamic cell structures to destroy tumor cells and cells infected by viruses.

"This new technology enables researchers to see individual elements previously below the physical limits of imaging using light," study leader Jordan S. Orange, M.D., Ph.D., who holds the Jeffrey Modell Endowed Chair in Pediatric Immunology Research at The Children's Hospital of Philadelphia, was quoted as saying.

Previously, microscopes could not "see" objects smaller than 200 nanometers (a nanometer is one-millionth of a millimeter). The STED microscope uses a unique arrangement of lasers and fluorescence to image fine structures, such as protein filaments, smaller than 60 nanometers.

Dr. Orange has researched the biology of natural killer (NK) cells at the immunological synapse -- the site where the NK cell attaches to its target cell and delivers cell-killing molecules. Filamentous actin (F-actin) is a crucial component of this process. F-actin is a structural protein in NK cells that forms a dense network through which cell-killing molecules called lytic granules move into the synapse.

Researchers previously thought that F-actin was not present at the center of the network, where granules are secreted through the synapse. However, under the super-resolution of the STED microscope, researchers found F-actin pervades the synapse but leaves openings just large enough to allow granules to pass through. "At the same time, F-actin appears to be dynamically interacting with the granules to move them toward their targets," Orange said.

Dr. Orange said further studies of NK function will investigate energy utilization and biological mechanisms that allow the lytic granules to navigate the immunological synapse. "As we better understand how this process is regulated, we will work toward manipulating immune response to treat immune deficiency disorders," Dr. Orange said.

SOURCE: Public Library of Science Biology, September 2011