This finding could help physicians predict whether children receiving such a transplant will experience either failure or significant delay in the reconstitution of the T cell population. Moreover, if the transplant is successful, T cells arising from donated stem cells will be available to launch attacks on the patient's cancer cells--the so-called "graft-versus-tumor" response. This will further improve the patient's outcome following initial therapy (chemotherapy, irradiation and surgery).
Physicians sometimes treat patients with stem cell transplants as part of therapy for a variety of diseases such as leukemia or sickle cell disease. In these cases physicians eliminate the patients' own stem cells that produce cancerous white cells or faulty red cells and replace them with healthy stem cells from donors. If the transplants succeed, the donated stem cells repopulate the blood with healthy red and white cells.
The St. Jude team showed that the more copies of tiny rings of DNA called signal-joint TRECs (sjTRECs) there are in a child's blood, the more likely it is that the patient's thymus gland can act as an efficient factory where stem cells become T cells. The thymus is an immune system organ behind the breastbone that processes immature "precursor" immune cells into specialized T cells.
T lymphocytes are specialized immune cells carrying proteins called receptors on their surface. The target that a T cell recognizes and attacks depends on the makeup of its receptor, which is constructed of protein building blocks. Each protein building block is coded by a specific gene. sjTRECs form
Contact: Bonnie Cameron
St. Jude Children's Research Hospital