Stem Cell Transplantation
Stem cells are immature cells that eventually develop into the various types of mature blood cells:
- Red blood cells, which carry oxygen
- Platelets, which help the blood clot
- White blood cells, which help fight infection
A stem cell transplant replaces defective or damaged cells in patients whose normal blood cells have been crowded out by cancerous cells. Transplants can also be used to treat hereditary disorders such as sickle cell anemia, or to help patients recover from or better tolerate cancer treatment.
Stem cells for transplant come from the following sources:
Autologous transplant: cells are taken from the patient's own bone marrow before chemotherapy and are then replaced after cancer treatment.
Allogeneic transplant: stem cells come from a donor whose tissue most closely matches the patient.
Umbilical cord blood from newborn infants is extracted from the placenta after birth and saved in special cord blood banks for future use. MD Anderson's Cord Blood Bank actively seeks donations of umbilical cords.
How are Possible Donors Identified?
Human leukocyte antigen, or HLA, typing is the method by which stem cell transplant patients are matched with eligible donors. HLA are proteins that exist on the surface of most cells in the body. HLA markers help the body distinguish normal cells from foreign cells, such as cancer cells.
The closest possible match between the HLA markers of the donor and the patient reduces the risk of graft versus host disease (GVHD). This condition occurs after transplant when your immune cells attack the donor cells, or when the donor cells attack your cells.
The best match is usually a first degree relative (children, siblings or parents). However, about 75% of patients do not have a suitable donor in their family and require cells from matched unrelated donors (MUD). These donors are found through registries such as the National Marrow Donor Program.
HLA typing is done with a blood sample taken from the patient, which is then compared with samples from a family member or a donor registry.