Research sheds new light on common bleeding disorder
Toronto, July 24, 2012
By Evelyn Jhung
Dr. John Semple
For the first time, research led by scientists at St. Michael’s Hospital is helping to explain the cause of a common blood disorder.
Usually, your immune system helps your body ward off infections and diseases. In patients with immune thrombocytopenia (ITP) – a blood disorder that causes bruises on the skin and bleeding – their immune system mistakenly attacks and destroys their body’s platelets, the blood fragments that stick together (clot) to stop bleeding. This is caused by a deficiency in the body’s T regulatory cells, which are produced in the thymus gland.
The reason for the deficiency is unknown – perhaps the thymus is not producing the cells or the cells are being destroyed after production. Or, as new research shows, T regulatory cells are being produced, but "instead of being released into the body where they are needed to prevent us from becoming autoimmune, they are being held up in the thymus," said Dr. John Semple, senior staff scientist, head of Transfusion Medicine Research and lead author of the study.
About one in 10,000 people have ITP, so "this is an important finding for this clinically significant disorder. If we can figure out how to release the cells from the thymus, we can look for better treatments for ITP," Dr. Semple said. Patients with ITP are treated with such therapies as steroids and intravenous gammaglobulin (IVIg) – therapies that increase platelet counts. Steroids have many adverse side effects and IVIg is a highly expensive option that is occasionally in short supply as it is so commonly prescribed. "If we can identify therapies that target the thymus, we have the opportunity to develop cheaper, more efficacious and less toxic ways to release the T regulatory cells from the thymus and treat ITP."
The study was conducted on mice. Dr. Semple and his team will be collaborating with researchers in Montreal who specialize in studying the thymus to investigate if the same holds true in humans. If so, there could be positive implications for other autoimmune diseases – such as rheumatoid arthritis, Type 1 diabetes and multiple sclerosis – that are associated with T regulatory cell deficiencies.
The study was published in Blood, a weekly medical journal published by the American Society of Hematology and the most cited peer-reviewed publication in the field.
About St. Michael’s Hospital
St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in more than 23 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, and care of the homeless are among the Hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Center, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael’s Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.