What Triggers Diabetes?

Scientists have plenty of evidence that people who develop the most severe form of diabetes harbor a genetic predisposition for the disease. But so far, they have not been able to pinpoint what triggers the deadly illness, in which the body's immune system destroys vital insulin-producing cells in the pancreas. One longstanding hypothesis got a big boost last week when researchers at Children's Hospital of Pittsburgh announced they had discovered compelling evidence that a virus is involved in Type I, or what used to be called juvenile diabetes. In their view, a viral infection causes the immune system to overreact and attack the pancreas. If confirmed, the finding could eventually lead to a vaccine for people with a family history of diabetes.

) The investigation grew out of unusually tragic circumstances. On two separate occasions, Dr. Massimo Trucco learned about a teenager who had died within a few weeks of developing diabetes. Trucco asked the parents for permission to perform autopsies, which showed direct evidence of an infection in the pancreas. More to the point, Trucco and colleagues found that the microscopic intruder had triggered an overwhelming immune response much greater than what was needed to subdue the virus. Unfortunately, the pancreas is particularly vulnerable to such an assault, and much of the tissue that produces insulin -- a hormone enabling cells to use sugar -- had been destroyed.

In effect, Dr. Trucco and his colleagues had caught both the virus and the immune system in their acts of destruction. Had the two patients lived longer, the infection would have subsided -- leaving only damaged tissue as an indirect clue that something had gone wrong.

Much work remains before people can benefit from these findings. Researchers have not yet identified the infectious culprit, nor do they know whether the virus is responsible for all Type I diabetes or just for a few unusual cases. But if the Pittsburgh researchers are right, and a vaccine can be developed, the disease could go the way of polio and other childhood scourges conquered by medicine.