Causes

Causes

Autoimmune Response

Type 1 diabetes is usually a progressive autoimmune disease, in which the beta cells that produce insulin are slowly destroyed by the body's own immune system. It is unknown what first starts this cascade of immune events, but evidence suggests that both a genetic predisposition and environmental factors, such as a viral infection, are involved.

Certain factors are thought to be important in this process:

• White blood cells called T lymphocytes produce immune factors called cytokines that attack and gradually destroy the beta cells of the pancreas. Important cytokines are interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma.
• Specific proteins are also critical in the process. They include glutamic acid decarboxylase (GAD), insulin, and islet cell antigens. These proteins serve as autoantigens. That is, they trigger the self-attack of the autoantibodies on the body's own beta cells.

Progression from the first stage, known as insulitis, to full-blown diabetes can take 7 years or longer. Unfortunately, by the time a person is aware that something is wrong and goes to the doctor with symptoms of type 1 diabetes, about 80 - 90% of the beta cells have been destroyed.

More than half of patients with insulitis do not develop diabetes. Researchers are greatly interested in discovering any factors that prevent the disease.

Genetic Abnormalities

Researchers have found at least 18 genetic locations that are related to type 1 diabetes. They appear to involve abnormal interactions among normal genes, mostly those known as I and II major histocompatibility genes, which affect the immune response.

The odds of inheriting the disease, however, are only 10% if a first-degree relative has diabetes, and even in identical twins, one twin has only a 33% chance of having type 1 diabetes if the other has it. Children are more likely to inherit the disease from a father with type 1 diabetes than from a mother with the disorder.