Cord blood banking is as much for the baby as it is for existing and future additions to the family. This is because there is not only an opportunity for the baby to use his or her own cord blood but also an increased chance it can be used by a brother, sister or other immediate family member.
Does the Disease Being Treated Matter?
The first factor on whether the cord blood can be used is the disease being treated. Some diseases can be treated using the baby’s own cord blood. When an individual uses his or her own stem cells, it is called an autologous transplant or infusion. Much of the promising research being conducted uses the baby own cord blood to treat conditions such as autism, cerebral palsy, stroke and more.
The whole family can possibly benefit from banking the baby's umbilical cord blood
Some diseases cannot be treated with the baby’s own cord blood. These conditions are often genetic. (I.e., the disease may have been present in the baby’s blood at the time of birth.) In cases where a baby cannot use his or her own cord blood, the cord blood of a sibling has a better chance of providing the lifesaving stem cells needed, making it important for families to bank the cord blood for all their children, including twins. When an individual uses another person’s stem cells, it is called an allogeneic transplant or infusion
Our page on cord blood–treatable diseases gives a full rundown of when the baby will be able to use his or her own cord blood or when he or she may need to use matching cord blood from another individual.
The disease being treated is an important factor in determining who can use the cord blood. Just as important is how well the donor cord blood matches the individual receiving the transplantation or infusion. Before a transplantation proceeds, the doctor will have the stem cells tested to make sure they are a HLA-match.
Deeper Dive into Matching
HLA-matching for a cord blood transplantation mainly looks at 4 or 5 loci, assigned the letters A, B, C, DRB1 and DQB1. With each loci, there are numbers that denote variations called alleles. There are more than 4,000 alleles for the A loci alone.
The baby inherits two pairs of each loci, one from the mother and one from the father. The A, B, C, DRB1 and DQB1 antigens are inherited together in what is called a haplotype.
For example, the child may inherit a haplotype from the mother with the following loci: HLA-A*2, HLA-B*5 HLA-C*1, HLA-DRB*3 and DQB1*1. The child will inherit another haplotype from the father.
What is HLA-Matching?
In 1958, scientists discovered a protein present on the surface of almost all cells that lets the body know if the cell is one of its own cells or a foreign cell. These proteins are called human leukocyte antigens (HLAs) and are what cause the immune system to respond to foreign cells like viruses and bacteria. This discovery expanded the use of stem cells beyond twins, leading to the first unrelated bone marrow transplant, in 1973.
These proteins stem from HLA genes, half which are inherited from the mother and half which are inherited from the father.
Cord blood often requires four out of six HLA markers to match to be eligible for a transplantation or infusion; on the other hand, a six-out-of-six match is most often required for a bone marrow transplantation.
In a haploidentical transplant, the donor and patient only need to have a 50% match as long as they are immediate relatives. This expands the use of cord blood to mom and dad and other partially matching immediate family members.
What is Graft-versus-Host Disease?
HLA-matching helps ensure the body accepts the new cells and the transplant is successful. It also reduces the risk of graft-versus-host disease (GvHD), which is when the transplanted cells attack the recipient’s body. The better the match—a six-of-of-six match is better than a four-out-of-six match—the better the outcome and the more likely any GvHD symptoms will be mild, if they suffer from GvHD at all.
Graft-versus-host disease occurs in 30%–50% of recipients when they aren’t a perfect match but the donor is still related. If the donor and recipient are not related, it increases to a 60%–70% risk. Unfortunately, GvHD also carries a 50% mortality rate.
Who Matches with the Baby’s Cord Blood?
In this simplified example of how HLA can be inherited, we can see the baby is match for one sibling and a half match for each parent. Unfortunately, the baby’s cord blood could not be used by the other sibling or any extended family members.
A baby’s own cord blood is always 100% match for the baby, making an autologous transplant or infusion the preferred method for treating many conditions because the risk of graft-versus-host disease is minimal.
Siblings—including 2nd or 3rd children
Because children receive one group of HLA markers from one parent and the other group from the other parent, siblings from the same parents have a 75% chance of being a perfect or partial match (25% chance of being a perfect match and a 50% chance of being a partial match) and another one-in-four chance of not being a match at all.
Each parent bestows one HLA group (haplotype) to their baby, so half the HLA markers come from the mother and half from the father. This means the child’s cord blood is always a 50% match for either parent. By the small chance the parents share HLA markers, the number of matching HLA markers between the child’s cord blood and his or her parents could increase beyond 50%. Even though parents are not usually more than a 50% match, they do have the ability to undergo a haploidentical transplant using the baby’s cord blood.
Half-siblings only share the HLA markers from one parent, and even then, they may not have received the same markers from that one parent. Outside the small chance the dad and step dad (or mom and step mom) are compatible on some level, half-siblings can only be up to a half-match. If the half-sibling is a 50% match, a haploidentical transplant would be possible.
Aunts and Uncles, Cousins and Grandparents
The farther you move away from the immediate family, the less compatible the child’s cord blood. Blood-related aunts and uncles and grandparents may have some compatibility, but it may be insufficient for transplantations especially as genetic recombination becomes a major factor in which genes are inherited.