CHICAGO, May 15 -- In one of the few studies of its kind, researchers from the University of Pittsburgh's Thomas E. Starzl Transplantation Institute have found that a subtype of dendritic cell plays a key role in preventing organ rejection and may be associated with transplant tolerance, the long-term survival of a transplanted organ without the need for immunosuppressant drugs.

Researchers will now be looking to see if the same cells are present in liver and kidney transplant recipients who have been successfully weaned off immunosuppression, patients who are essentially tolerant of their organs.

The findings are significant because dendritic cells, a rare type of white blood cell that is present in all tissues, have been thought only to be involved in prompting the rejection process, reported Peta J. O'Connell, Ph.D., at Transplant 2001, the joint meeting of the American Society of Transplantation (AST) and the American Society of Transplant Surgeons.

Dendritic cells are known for their ability to identify and present antigens, or foreign substances, to other immune system cells that are programmed to destroy the antigen. But according to Dr. O'Connell, some dendritic cells apparently regulate the immune response, determining that a frontline attack by T cells can be unwarranted.

Dr. O'Connell, a visiting research instructor working with Angus W. Thomson, Ph.D., D.Sc., reported that a pre-transplant infusion of lymphoid dendritic cell subtypes derived from tissue such as the spleen, allowed for prolonged survival in a mouse heart transplant model, even without the use of drugs to control rejection. In contrast, myeloid dendritic cells accelerated the rejection response.

"The lymphoid-derived dendritic cells somehow disarm immune system T cells from doing their part to attack the donor organ possibly by causing either their death or limiting their proliferation," explained Dr. O'Connell, who received an AST Young Investigator's Award for her wor
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Contact: Lisa Rossi
rossil@msx.upmc.edu
412-647-3555
University of Pittsburgh Medical Center
14-May-2001