Dr. Pandelakis Koni, immunologist, has developed a conditional knockout mouse in which cellular communication that triggers the immune response to an invader can be selectively stopped. His mouse is featured in a special February issue of Genesis: The Journal of Genetics and Development, which contains 43 papers documenting the development of new animal models available for use by researchers across the world.

Dr. Koni is studying a type of surveillance cell called dendritic cells that stand on patrol throughout the body looking for invaders. "If you have an infection or some foreign agent in your body, dendritic cells detect it and are very good at picking it up and delivering it to the right place to switch on your immune system," he said. "They literally eat up bacteria, put them inside their vesicles, where a lot of acids and digestive enzymes chop them up. Eventually, a small piece of protein from the bacteria makes its way to the surface of the dendritic cell," he explained.

This is where Dr. Koni interrupts the process. Dendritic cells have on their surface major histocompatibility complex molecules, or MHC molecules, that take up these pieces of protein and literally hold them up for another immune system cell called T cells. "The T cell comes along with its own surface protein which is designed so it can survey that surface." Those T cell receptors lock onto the MHC molecule on the dendritic cell. The T cell then switches on, begins to proliferate and determines what other immune components it needs to summon.

"The conditional knockout we made enables us to eliminate the MHC molecule from different types of dendritic cells," Dr. Koni said. The four general types of dendritic cells are Langerhans' cells prima
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Contact: Toni Baker
tbaker@mail.mcg.edu
706-721-4421
Medical College of Georgia
13-Feb-2002