Each day, viruses attack the immune system looking to gain a foothold in the body and cause sickness. But the immune system regularly turns away these invaders by using antibodies and killer T cells that attack the antigen. Until now, scientists only knew these that events happened, but not how or why.
A research team at National Jewish Medical and Research Center led by Philippa Marrack, Ph.D., and John Kappler, Ph.D., report in the April 28 issue of Science that they have discovered how certain proteins work together in the immune system to control the T cells that attack viruses such as chicken pox, measles and other diseases.
National Jewish researchers have shown that the proteins IL-15 and IL-2 work together to balance the immune response against antigens. Researchers found that IL-15 drives the production and division of memory killer T cells and IL-2 kills these T cells as they divide.
"Memory" T cells are the immune system's primary defenders against antigens. When the immune system first comes in contact with an antigensuch as the viruses that cause chicken pox, measles or polioit creates killer T cells that then turn into "memory" T cells. If and when the antigen invades the immune system a second time, these "memory" T cells recognize the invader and bind to it, killing the antigen more quickly than during the first exposure. "You get a nuclear holocaust, not just gunfire," said Dr. Marrack, a National Jewish researcher who studies the inner workings of the immune system. (This is why people don't get chicken pox, measles or similar immune diseases more than once.)
Still, researchers were unsure if T cells maintained the ability to remember antigens from one exposure to anotherthere could be decades between exposuresby laying in wait, by being exposed to antigens regularly or by holding on to small parts of the virus. Recently, National Jewish researchers found that none of these explanations were quite right. Rather, "memory" T ce
Contact: Jordan Gruener
National Jewish Medical and Research Center