Stem cell transplantation can be defined as a process by which stem cells from the patient or a donors bone marrow are removed and re-infused into the patient to produce healthy blood cells (Australian Academy of Science, 2001). Stem cell transplants may be allogeneic, syngeneic or autologous. The most common sources for such transplants are bone marrow, blood and umbilical cord or placental stem cells (Gross & Johnson, 1998. )
Bone marrow transplantation (BMT) is a procedure wherein the bone marrow, which has been destroyed subsequent to chemotherapy or radiation, is replaced with healthy bone marrow. Peripheral blood stem cell transplantation (PBSCT) involves replacing blood-forming cells destroyed by cancer treatment with immature blood cells (stem cells), which helps the bone marrow to recover and produce healthy blood cells as before (NCI, nd). Transplantation may be of three types (Rosenbaum & Rosenbaum, 2005):
a. Autologous transplants, wherein patients have their own healthy bone marrow cells removed and stored till the time of transplant. Later, chemotherapy, and radiation in some cases, is administered to destroy any remaining diseased cells.
b. Syngeneic transplants, wherein patients receive stem cells donated by their identical twin (monozygotic twin). In this case, in addition to HLA, all other genetic loci are also matched (Carella et al, 2001.). Although the development of GVHD can be avoided, the risk of relapse is greater in patients with leukaemia. This is due to the lack of GVL effect (Yarbro, Frogge & Goodman, 2005.)
c. Allogeneic transplants, where patients receive stem cells donated by their brother, sister or parent (related allogeneic transplant) or an unrelated donor (unrelated allogeneic transplant). In order to find a potential donor, Human leukocyte antigen (HLA) testing has to be performed.
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