World map of family banks
- Processing: How is cord blood processed before storage?
The three main components of cord blood, like any blood collection, can be separated by weight: the heaviest layer is the red blood cells (RBC), the lightest is the plasma (a clear white liquid), and in the middle is a pinkish layer called the "buffy coat" which contains the white blood cells (WBC), including stem cells. When banks process the cord blood, the final separated component that goes into storage is the buffy coat, even though only about 1% of the cells are actually stem cells. There is no procedure to separate out the stem cells alone.
The vast majority of blood processing methods rely on the different density of the three main blood components. They can be separated by sedimentation, or by centrifuge, or by a combination of the two techniques. The procedure can be performed manually by trained technicians or by automated machine.
- If I banked privately for one child, do I need to do it for additional children?
All the reasons that you banked for the first child are still valid for additional children.
1. If you want the baby to have the option of using his/her own cells, then you need to bank them.
2. If you are banking to cover siblings, then the ability to use cord blood from one child for another depends on whether they have matching HLA type. Two full siblings have a 25% chance of being a perfect match, a 50% chance of being a half match, and a 25% chance of not matching at all. For a cord blood transplant, donor and patient must match at 4 out of 6 (67%) HLA types. The more siblings with banked cord blood, the more chance that they cover each other for possible transplants or other therapies for which sibling stem cells are accepted.
Odds of sibling match are based on haplotype inheritence: that the child will receive 3 HLA types as a group from each parent.
- Processing: Must cord blood be processed before storage?
The earliest cord blood transplants were performed with whole cord blood. Thus, it is not absolutely necessary to process cord blood in order to save patient lives. There has never been a prospective randomized trial to compare transplant patient outcomes with cord blood that had been stored whole versus processed.
Most cord blood banks, both public and private, now process cord blood to remove both the plasma and the red cells, and cryo-preserve the remaining buffy coat holding stem cells. Some banks also save the removed red cells and plasma in companion storage. Some banks save a sample of maternal blood.
The removal of plasma is also called volume reduction. The volume reduction enables more collection units to fit in a freezer and requires less cryogenic nitrogen per unit.
Also, the majority of banks remove red blood cells prior to freezing, primarily because these cells often burst during freezing and release iron from hemoglobin that can be toxic. The alternate to removing the red cells before freezing is to wash any broken cells out of the collection upon thaw. Removing the red cells also removes the donor's blood type (the ABO and Rh types). When cord blood goes from a donor to a patient for a transplant, the donor and patient can be compatible on all the HLA types used for transplant matching and still have incompatible red blood types.