Juvenile Diabetes Breakthrough–Destruction of Insulin Producing Cells Witnessed
Researchers from Washington U School of Medicine ( St. Louis) working on diabetic mice have discovered in great detail the immune system cells that are the likely cause of type 1 diabetes. Scientists were able to look at the immune system cells from insulin-producing cells in the pancreas known as the islets of Langerhans. They observed the immune system cells, known as dendritic cells, in the process of destroying insulin making structures and carrying away fragments of insulin-producing cells known as beta cells. This discovery is a huge step toward understanding the immune system destruction of the beta cells in the pancreas which is the type 1 diabetes cause.
Having isolated dendritic immune system cells from the pancreas scientists can now focus on why they attack the normal cells in the pancreas. Preventing this immune system attack on the pancreas beta cells could prevent juvenile diabetes (also called type 1 diabetes). Emil R. Unanue, M.D. indicates that this discovery may allow us to find ways to inhibit dendritic cell function in order to prevent type 1 diabetes from developing in susceptible individuals.
The American Diabetes Association states that as many as 2 million people in the US have type 1 diabetes, which is also called juvenile diabetes because the condition often starts in childhood (in contrast to type 2 diabetes which is a different disease process and occurs in adults) .
People with type 1 juvenile diabetes must have insulin shots to survive because their immune system has destroyed the islets of Langerhans, which produce insulin. Insulin is required by the body to allow cells to use and store glucose from the bloodstream.
Researchers have been aware that dendritic cells are presentation the islets of diabetic patients for a long time. Dendritic and other antigen monitoring cells are the sentinels of the immune system: They look for fragments of protein in the the body and start the immune response by lymphocytes to attack foreign substances. The lymphocytes lead immune attacks against foreign proteins on bacteria and viruses and eliminate them, clearing infections. At times, the immune system cells can get mistakenly get activated and attack the patients normal cells causing autoimmune diseases such as type 1 juvenile diabetes or rheumatoid arthritis.
The dendritic cells’ presence in the islets and their ability to start immune attacks made them suspects in type 1 juvenile diabetes. Due to their small size and being few in number has made it tough to observe the role that they played in the development of diabetes.
“They’re very tiny and there are only about 5 to 10 of them per islet, each of which contains approximately a thousand cells,” explains Dr. Unanue. “So the senior postdoctoral researcher in the lab who did this work, Boris Calderon, had to develop some sophisticated cellular assays to pick them up.”
Calderon, M.D., found indications that the cells were carrying granules of insulin and pieces of proteins from beta cells on their cell surfaces. To test whether this cargo carried by the dendritic cells had the potential to trigger an immune attack on beta cells, Calderon exposed the dendritic cells to lymphocytes taken from diabetic mice. The lymphocytes were activated by the dendritic cells of the islets and switched into attack mode.
In a separate line of research, Unanue’s lab has learned that dendritic cells in the pancreas may normally have beneficial effects on the health of beta cells. They’ve shown that when dendritic cells are absent from the pancreas, the beta cells are smaller, an indication that they’re not as healthy.
“We think these dendritic cells aren’t in the pancreas by accident,” says Unanue. “We believe that in the normal individual they help maintain the health of beta cells. But in a person with autoimmune diabetes, they appear to start the problems that destroy beta cells.” Determining which patients are at risk and how the mistaken activation of the immune system occurs are the next goals of the researchers. Ultimately such research may one day lead to cure for type 1 diabetes.
ref: http://www.ncbi.nlm.nih.gov/pubmed/18427107 and http://mednews.wustl.edu/news/page/normal/11751.html
