What is allogeneic transplant?

In allogeneic transplants, blood stem cells donated by another individual are infused into the patient. Allogeneic transplants are performed for the following diseases: 

• Immunodeficiencies
• Leukemias (various types)
• Blood and marrow failure syndromes (severe aplastic anemia)
• Inborn errors of metabolism
• Sickle cell disease
• Alpha Thalassemia
• Beta Thalassemia

Finding a donor

The blood stem cells may come from bone marrow, peripheral blood or cord blood. The donor can be related, such as a sibling or parent, or unrelated. Your child's donor may be:

• A tissue-type matched sibling
• A partially matched parent
• An unrelated donor
• Unrelated cord blood

Siblings of the child requiring the transplant have a 1 in 4 (25 percent) chance of being a match to the patient. That is not a guarantee that if you have 4 children, one will be a match.

Occasionally the child's parent can be a good match, but that is not common.

HLA typing

A test known as HLA typing, or tissue typing, determines the best-matched donor. HLA stands for human leukocyte antigens. These are proteins found on the surface of most cells in the body.

The immune system uses HLA to recognize what is the body's own cell, and what is a foreign cell. Finding a well-matched donor is important to reduce the risk of host-transplant complications. Learn more about HLA testing.

Related donors

If a sibling is a match, your child's doctor will discuss the collection process. Stem cell collection is generally a very safe process; it has been done safety for more than 35 years. The risks may include: infection, which is very rare; blood loss; and the risks associated with general anesthesia. 

Unrelated donors

Unrelated donors are located by the Blood and Marrow Transplant Program through the National Marrow Donor Program's Be The Match Registry, and other blood and marrow or cord blood registries.

These registries make it possible to find well-matched donors for most of our patients who need an allogeneic transplant. It may take weeks to months to find an unrelated donor.

We also have special methods to process unrelated marrow or peripheral blood to reduce the risk of certain complications. 

Cord blood

If there is no HLA-matched sibling, cord blood transplant may be considered. Cord blood is collected from the umbilical cord and placenta at birth, and does not harm the infant.