Stem cell transplants are used to treat cancers such as leukemia, lymphoma, and myeloma, which affect the bone marrow where blood cells are made. Stem cell transplants are also used to treat certain immune system diseases and other conditions. If you or a loved one will have a stem cell transplant, here are some helpful terms to know.
Types of stem cell transplants
Allogeneic transplants use stem cells from a donor whose tissue closely matches the patient’s tissue. This type of transplant helps the patient form a new immune system.
Autologous transplants use stem cells that come from a patient’s own blood or bone marrow. The stem cells are collected before the patient begins treatment such as chemotherapy or radiation therapy that can destroy stem cells. The decision whether to use an allogeneic or autologous transplant is based on many factors, including the type of cancer and the patient’s health.
Bone marrow transplant is an out-dated term for stem cell transplant. In the past, stem cells were primarily collected from the bone marrow, but now they are usually collected from the blood.
Parts of the body
The bone marrow is a sponge-like tissue found in the center of some bones. Red blood cells, white blood cells, and platelets are made in the bone marrow.
Human leukocyte antigens (HLAs) are proteins found on the surface of most cells. The immune system uses HLAs to tell which cells are the body’s own normal cells and which are abnormal (such as cancer cells) or come from outside the body (such as donor stem cells). Doctors use HLA tests to find a stem cell donor with HLAs that closely match the patient’s.
The immune system helps the body to fight infection and includes organs, tissues, cells, and substances made by the body. For example, the tonsils, bone marrow, lymph nodes, and white blood cells are all part of the immune system.
Platelets are found in the blood. They help blood to clot.
Red blood cells carry oxygen to every part of the body.
Stem cells are cells from which other types of cells form. For example, hematopoietic stem cells are formed in the bone marrow and later develop into blood cells.
Umbilical cord blood from newborns can be used in allogeneic stem cell transplants for patients who do not have a related or matched unrelated donor (see below). This blood is taken from the cord and placenta after a baby is born. MD Anderson has a cord blood bank that accepts donations of umbilical cord blood (see box).
White blood cells help the body to fight infection. Neutrophils and lymphocytes—such as T cells, B cells, and natural killer cells—are among the types of white blood cells.
Types of donors
A first-degree relative is a person’s parent, child, brother, or sister. First-degree relatives are usually the best people to donate stem cells to a patient who is having an allogeneic transplant.
A matched unrelated donor is not in a patient’s family but has HLAs similar to the patient’s.
Transplant-related treatments and conditions
Conditioning regimens are courses of chemotherapy and/or radiation therapy often given before a stem cell transplant. These treatments kill cancer cells in the body and destroy existing bone marrow to make room for bone marrow created by the new stem cells. In allogeneic transplants, these regimens may include immunosuppressive drugs (see below).
Graft-versus-host disease (GVHD) happens when stem cells from a donor harm the normal tissue of a patient who has received an allogeneic stem cell transplant. Doctors are careful to choose stem cell donors who have tissue similar to the tissue of the patient receiving a stem cell transplant so that GVHD will be less likely.
Immunosuppressive drugs suppress the body’s immune system. They may be given before or after an allogeneic transplant to prevent GVHD or after GVHD occurs.
Myelosuppression, which results from conditioning regimens, is a decrease in bone marrow activity that causes low levels of red blood cells, white blood cells, and platelets. Severe myelosuppression is called myeloablation.
Be sure to ask your medical team to explain any terms they use that aren’t familiar to you. Your team will be happy to help.
For more information, ask your physician , call askMDAnderson at 877-632-6789, or visit www.mdanderson.org.
OncoLog, February 2017, Volume 62, Issue 2
Donate Stem Cells or Cord Blood
If you live anywhere in the United States and are interested in donating stem cells, visit www.bethematch.org.
If you are pregnant, in the Houston area, and interested in donating umbilical cord blood when your child is delivered, call 713-563-8000 or 866-869-5111 or email email@example.com.