New predictor for blood transplant success

The success of blood stem cell transplants used to treat diseases such as leukemia, Hodgkin’s lymphoma and aplastic anemia may soon become more predictable, thanks to a discovery made by researchers at the University of British Columbia.

Donor blood stem cells -- cells that can produce red and white blood cells and platelets -- are injected into a recipient to produce new blood.

UBC scientists have identified a “molecular flag” that can help determine if T-cells – cells that drive the body’s immune response – will be produced by the thymus following a blood stem cell transplant. T-cell progenitors, or master cells, are manufactured in bone marrow but must migrate to the thymus, an organ located near the heart, in order to mature into functional T-cells.

A common problem with blood stem cell transplants is the failure of progenitor cells to repopulate the thymus and generate T-cells. Without T-cells the patient is unable to fight infection and post-transplant prognosis is poor.

“We now have a signal that gives us critical information about how the body will respond to blood stem cell transplants,” says principal investigator Fabio Rossi, UBC assistant professor of medical genetics and Canada Research Chair in Regenerative Medicine. “This gives us a molecular handle on whether the thymus will be receptive to migrating T-cell progenitors.”

Rossi, along with Hermann Ziltener, a UBC professor of pathology and laboratory medicine, found that a molecule called P-selectin increases if the thymus is ready and able to accept migrating T-cells. Scientists refer to successful migration as passing through the “thymic gate.” By tracking P-selectin, scientists can now detect if thymic gates are open or closed.

This research marks the first description of the thymic gate mechanism and was published recently in Nature Immunology. Rossi and Ziltener work at UBC’s Biomedical Research Centre.

There are approximately 150 blood stem cell transplants in B.C. every year. The survival rate ranges from 25-75 per cent, according to the Leukemia/BMT Program of British Columbia.

Researchers estimate that it would be at least five years before the discovery can be translated into a clinical test.

For more information about bone marrow transplants, visit www.bloodservices.ca.