The Policing Cell
Scientists that have been studying macrophages at the University of Pennsylvania have made an interesting discovery. Macrophages are the biological cells that spring from white blood cells to eat and destroy foreign or dying cells. Their recent discovery has uncovered information concerning how these cells differentiate between friend and foe.
The researchers studied these macrophages, labeled “policing cells”, by looking at how they choose to attack and engulf foreign cells and particles but at the same time recognize and refuse to eat their own kind. They discovered their behaviour was similar to that of a police dog in that the macrophage responds to a signal that means ‘let go’. The scientists summed this up by saying “It’s what makes your body more of a 'dog eat cat' kind of world rather than a 'dog eat dog' world.”
The team observed macrophages in culture using ‘friendly’ human blood cells and ‘foreign’ sheep blood cells as well as plastic particles. In all cases, the macrophage binds to a target, often identified by a cloak of common IgG antibodies, and ‘frisks’ the target with a cell extension. This protein extension becomes a muscle-like headlock with foreign targets, wrapping around the target and pulling it in. Self-cells have a molecular protein on their surface that is specifically recognized by the macrophage to switch off the headlock, thus stopping engulfment and allowing self cells to coexist and move on.
This discovery has caused a degree of excitement as scientists may now be able to use this knowledge of macrophages in various ways. Rogue macrophages are the root cause of the many inflammatory diseases such as arthritis, they also provide the mechanism for tissue and organ rejection after transplant. There is also evidence that some types of cancer cells over-express the molecular protein that macrophages recognize as friendly, like a fake ID, which allows the cancer to avoid being perceived as a target. By understanding how these ‘policing cells’ differentiate between a target and a non-target scientists may now be able to use this information to look at new ways to assist in medical research.
For more information see: http://www.sciencedaily.com/releases/2008/03/080311141021.htm
The full paper can be found as the cover article in the March 10 edition of the Journal of Cell Biology.
Posted by Matthew O'Gorman 41006890
