Cord blood, collected from the placenta and umbilical cord after birth, is a rich source of stem cells. These include hematopoietic stem cells, which can develop into all types of blood and immune cells. Its unique properties have led to its established use in therapies for the child themselves or other family members.
The HLA Matching Barrier
A primary consideration for successful stem cell transplantation is compatibility between the donor and recipient, determined by Human Leukocyte Antigens (HLA). These proteins are found on the surface of most cells and help the immune system recognize which cells belong. A close HLA match is necessary to minimize the risk of the recipient’s immune system rejecting the transplanted cells or the transplanted cells attacking the recipient’s body, a complication known as Graft-versus-Host Disease (GVHD).
Children inherit half of their HLA markers from each parent, making a parent a “half-match” or haploidentical to their child. A perfect, full HLA match between a child’s cord blood and a biological parent is statistically rare, occurring in only about 1% of cases. This presents a significant immunological hurdle for parental transplants. While cord blood stem cells are more tolerant of some mismatches than bone marrow, sufficient HLA compatibility is still important for a safe outcome.
When Cord Blood Can Be Used for Parents
Despite the rarity of a perfect HLA match, there are specific circumstances where a child’s cord blood can be used for a parent. One scenario involves haploidentical transplants, where a parent serves as a half-matched donor. Advances in transplant protocols, such as post-transplant cyclophosphamide, have made these partially matched transplants increasingly viable by helping control the immune reaction. This approach widens the pool of potential donors for adult patients who might not have a fully matched sibling or unrelated donor.
A recent development involves “haplo-cord” transplants, combining cells from a haploidentical bone marrow donor with cord blood stem cells. This dual approach offers benefits such as faster engraftment, where new stem cells begin producing blood cells, and a reduced risk of severe GVHD. The inherent immaturity and flexibility of cord blood stem cells contribute to their use in these partially-matched settings.
Diseases Potentially Treatable
When a suitable match and clinical indication are present, cord blood stem cells can treat a range of conditions. These include blood cancers, such as leukemias and lymphomas, where stem cells replace diseased blood-forming cells. Inherited blood disorders, like sickle cell anemia, thalassemia, and Fanconi anemia, also benefit from cord blood transplantation by replacing faulty cells with healthy ones.
Cord blood also treats certain immune deficiencies, such as severe combined immunodeficiency (SCID), by helping rebuild a functional immune system. Some metabolic disorders, including Hurler’s syndrome and Krabbe disease, are also treatable with cord blood transplantation. The effectiveness of cord blood in these treatments depends on factors like the specific disease, patient health, and compatible stem cell unit availability.