March 7, 2005
by Alison Davis

Our world is teeming with potential health threats in the form of bacteria and viruses. Standing guard is the body's first line of immune defense, the innate immunity system. Despite the system's importance, researchers know relatively little about how innate immunity works. However, they have recently learned that the core molecular elements of innate immunity appear remarkably alike in organisms as diverse as plants, insects, and people. Thus, researchers are poised to answer key questions about this process by doing experiments in simple organisms.

In a recent example of the benefit of such an approach, Patrick O'Farrell, Ph.D., of the University of California, San Francisco, used laboratory fruit flies to search for fundamental clues about innate immunity. Harnessing the power of the revolutionary gene silencing technique called RNA interference (RNAi), which was featured in last year's story of discovery, O'Farrell used robotic methods to rapidly and systematically inactivate each of more than 7,000 fruit fly genes that are close counterparts of genes in humans and animals. He then identified those genes whose loss had a recognizable impact on the insects' ability to fight off germs. The strategy paid off, and O'Farrell discovered two fruit fly genes that are involved in carrying out the basic functions of innate immunity.

Since the fruit fly genes bear close resemblance to human genes, this work should quickly yield insights about how the proteins encoded by these genes function in human innate immunity. O'Farrell's findings are significant in another important way, as well. The results lend support for using RNAi to investigate complex molecular networks, which are known to be central to the function of both healthy and diseased cells.