Types of Blood & Marrow Transplants
Allogeneic blood or marrow transplant replaces damaged bone marrow with healthy donated marrow. Usually, the donor is a family member whose bone marrow closely matches the patient’s. Sisters and brothers have about a 1 in 4 chance of matching each other. In some cases no one in the family has bone marrow that matches the patient. We can look for a donor through the National Marrow Donor Program and other registries. A blood test called HLA-tissue typing is done to determine how closely the patient and donor tissues match each other.
Autologous blood or marrow transplant uses some of the patient’s own blood or marrow which can be frozen and stored for use later. It is used to “rescue” the bone marrow after high dose chemotherapy or radiation.
Syngeneic blood or marrow transplant uses an identical twin's bone marrow for the donor marrow.
Cord blood from a sibling or an unrelated donor can be used but must be matched just like bone marrow. These types of transplants are for much smaller patients due to a smaller amount of stem cells collected.
A haploidentical transplant uses marrow or stem cells from a relative who is only a partial match. Children inherit protein markers from their parents called Human Leukocyte Antigens (HLA). Half are inherited from their mother and the other half are inherited from their father. These antigens are important in transplantation and should be the same for the donor and patient.
Haploidentical donors share one haplotype (an identical set of HLA antigens from a family member) and are mismatched for at least one antigen on the other haplotype. Thus haploidentical transplants have traditionally been considered very risky. Because the donor and patient are not a perfect match, haploidentical transplants are often complicated by severe graft-versus-host disease (GVHD), rejection of the transplant or poor recovery of the immune system. Yet, haploidentical transplants remain an option for some patients who have no other possible donor.