Antibodies and white blood cells called lymphocytes are nature's front-line soldiers in the defense against disease, but they do not always mount a fair fight.
Sometimes these immune system components play cruel tricks on the very people they are supposed to protect, rendering a person helpless against the aggressiveness of a disease-fighting system gone awry.
Such has been the scenario in rheumatoid arthritis, pernicious anemia and lupus erythematosus.
New studies suggest that an immune system bent on destroying insulin-producing cells in the pancreas may be the cause of type 1 diabetes, which usually begins in childhood and is the most serious but least common kind of diabetes.
Insulin Not Produced
Diabetes is a disorder in which the body does not produce or properly use insulin, a hormone needed to convert sugar and starches into the energy needed for daily life.
The disorder predisposes its victims to atherosclerosis, high blood pressure, kidney failure, coma and blindness. It is blamed on the deaths of more Americans each year than all other diseases except cancer and heart problems.
Type 1, which occasionally is diagnosed in adults, involves the complete shutdown of insulin production and always requires insulin injections to control blood sugar levels. Insulin, however, does not cure the disease or even prevent its life-threatening complications.
The American Diabetes Assn. estimates that about 1 million of the 11 million diabetics in the United States suffer from type 1.
Type 2, however, does not require insulin injections, is most often seen in obese adults and can be controlled with drugs and diet. Scientists are certain that this form of diabetes does not involve an apparent immune system attack on pancreatic cells.
Evidence shows that people who develop the insulin-dependent type of diabetes do so because they inherit a susceptibility. But possession of the genetic vulnerability alone is not enough to trigger the disease.
Scientists are finding that a host of viruses and even toxic substances may prompt the insidious immunologic destruction of pancreatic cells.
"We now have a greater understanding of what causes insulin-dependent diabetes," said Dr. Mitchell Geffner of the UCLA School of Medicine.
"But despite this new information there are still a lot of gaps in our understanding of diabetes, and there is still no one therapy that can reverse or slow down the disease," he said.
Doctors who treat children with the disorder say the cellular destruction is so painless that parents are unaware that their children are sick until the symptoms appear--excessive thirst, frequent urination, weight loss and general malaise.
"We now know that the whole evolution of the disease may take many years," Geffner said. "Usually, by the time symptoms of the disease manifest, the destruction of pancreatic beta cells has been under way for a very long time."
Blood Sugar Level Soars
Beta cells are involved in the manufacture of insulin. Without them, there can be no insulin production, and without insulin, blood sugar levels soar and diabetes ensues.
The killer immune system cells called lymphocytes and protein antibodies can home in on the islets of Langerhans, groups of cells in the pancreas where beta cells reside and insulin is produced.
Immune system components are attracted to beta cells because they mistakenly recognize them as foreign, destroying them in a process akin to a biological Pac Man that consumes the hormone-manufacturing cells until their population is decimated.
"There's no question that type 1 diabetes is now very much considered an autoimmune disease," said Dr. Ronald Kahn, medical director of the Joslin Diabetes Center in Boston.
"All of these patients have antibodies to their own islet cells," he explained. "So the hope is that if one can catch the disease early in its course and suppress the immune destruction, it will be possible to prevent diabetes from appearing.
Early Detection Stressed
"But, of course, all of this would depend on how early detection and treatment begin."
Scientists are finding that telltale markers, the genes of certain chromosomes, may be associated with a predisposition to type 1 diabetes.
The markers are found in 95% of all type 1 diabetics. And new studies suggest that millions of Americans--possibly 50% of the entire population--possess these markers, known to scientists as DR3 and DR4.
Dr. Steven Schoenfeld, a diabetes researcher at the University of Washington, Seattle, thinks additional research eventually will produce more specific markers for diabetes.
"The DR3 and DR4 markers are frequently found in people with Graves disease and some forms of arthritis," he said. "These genes predispose to other autoimmune diseases, so we're looking for more specific gene markers (for diabetes) that a smaller percentage of the population will have."