HEALTH Researchers protect mice from disease

An underchallenged immune system produces too few T cells, researchers say.
SCRIPPS HOWARD
In one of the most powerful demonstrations yet that immune cells need to be stimulated to keep from turning against the body's own tissues, researchers report they were able to protect mice predisposed to become diabetic by exposing them to germ fragments.
In a report published Thursday in the journal Cell, scientists at The Scripps Research Institute in La Jolla, Calif., said they were able to boost the supply of critical T cells and curtail development of insulin-dependent diabetes in mice genetically cued to develop the autoimmune disease.
The team, led by immunologist Nora Sarvetnick, reported a surge in the T-cell count when the mice were challenged with a mixture of bacterial cell-wall components.
"Autoimmunity has been considered a condition of too much stimulation," Sarvetnick said. "What we are seeing is that it is a condition of too little stimulation."
Sarvetnick and her colleagues argue that humans and other animals need a certain level of immune-system stimulation to keep the defensive cells functioning properly.
Otherwise, the underchallenged immune system produces too few T cells. The body then tries to correct this by expanding this supply on its own, creating cells more likely to turn against the body itself, particularly if growth signals are disrupted or the T cells are depleted by certain viral infections.
Diabetes development
Type 1 diabetes develops when T cells turn against critical cells in the pancreas, the body's source of insulin. Sarvetnick and others think this is often triggered by a common viral infection of the pancreas. Without insulin, the glucose in the bloodstream increases; without insulin treatment, this can lead to nerve and kidney damage, reduced eyesight and increased risk of blood-vessel degeneration and heart disease.
Sarvetnick and her team said their theory would explain why childhood bacterial infections decrease the risk for developing autoimmune diseases like Type 1 diabetes, rheumatoid arthritis, lupus and even asthma, and why incidence of these diseases has been on the rise in less-germ-tolerant, developed countries during the past 50 years compared to less-developed nations.