February 18, 2015

When it comes to any kind of transplant, whether it be blood, stem cell, organ or tissue, the donor and the recipient must be compatible, or a genetic “match,” with one another in order for the transplant to be a success. But what does that mean?

First, it’s important to understand the basic make-up of the blood. Blood type (A+/-, B+/-, AB+/- and O+/-) is a commonly known concept, but there’s more to being compatible than a matching blood type. The HLA type of the blood must be correct too. HLA stands for Human Leukocyte Antigen. HLA is a protein marker in the blood that is found in all the cells of your body. These markers tell your body that the cell is a part of you and that it belongs. Cells that your body identifies as not having your specific markers are considered foreign bodies and your immune system goes to work to kill or reject them. Each cell has 6 of these unique markers, half of which you get from your mother, half from your father. It is a complex and detailed lab test that is done to determine a person’s HLA type.

Cord blood recipients do not need to be as exact a match in order for the blood to be considered a match. Because of the young nature of cord blood stem cells, they are more immature and easier to adapt when introduced into a new environment. For a cord blood transplant, a person would only need to be a partial match, with 4 out 6 markers the same. For any other kind of stem cell transplant, an exact match is required.

The matching HLA types are necessary for several reasons. For one, it increases the likelihood that the transplant will not be rejected by your body. When that happens, it is called Graft vs. Host Disease, which is a potentially serious complication of transplants. GVHD is a fairly common occurrence in transplants coming from someone else. It comes in different degrees of severity and when it occurs, the body tries to fight off the new blood or organ as if it is harmful. Fortunately, because cord blood is immature, a transplant with it is less likely to result in GVHD.

Another positive to cord blood transplants is that the cells are more likely to engraft, or grow, in its new location. The cells are smart. They seek out the sick or damaged cells and multiply in order to replace or repair them.

Cord blood banking takes out a lot of the uncertainty, when it comes to finding a matching donor, should someone in your family need a cord blood transplant. When you store your baby’s cord blood in a cord blood bank, you do so knowing that the blood will always be a match for him or her. Also, in some cases a transplant from someone else is preferred, depending on what is being treated, and in that case, the blood of a sibling is usually the best option to try. Siblings have a 1-in-4 chance of being a perfect match. Parents also are considered half matches to their children, since half of the baby’s DNA makeup comes from each parent.

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