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HLA matching

HLA matching is used to match patients and donors for blood or marrow transplants. It’s much more complicated than blood typing. For HLA matching:

  • You and potential donors will have blood drawn
  • The blood is tested in a lab to figure out your HLA type
  • Your HLA will be compared to potential donors to see if there is a match

There are many HLA markers. Each HLA marker has a name. The names are letters or combinations of letters and numbers.

Sometimes, it’s hard to find a match because some HLA types are less common. HLA types are inherited so siblings can sometimes be a match for each other. Each of your brothers and sisters who has the same mom and dad as you has a 1 in 4 chance (25%) of being a complete, or full, match. You’re more likely to match someone with a similar ethnic background or ancestry.

Use HLA to choose the best donor or cord blood unit (CBU)

Your doctor wants to find the best possible donor or CBU for you. Usually, it’s a donor or CBU whose HLA are very closely matched to yours.

A close match is important because it:

  • Improves the chances for a successful transplant.
  • Helps your donor cells engraft (grow and make new blood cells in your body).
  • Reduces the risk of complications like graft-versus-host disease (GVHD). GVHD happens when the immune cells from the donated cells (the graft) attack the recipient’s cells (the host).

There are times when a closely matched donor isn’t the best option. For some patients, a donor who matches exactly half of their HLA is best. This is called a haploidentical (or half-matched) transplant.

Rules for HLA matching

There are rules for the minimum, or lowest, HLA match needed between a donor and patient. Research shows that patients have better outcomes (results) with a closely matched donor. Sometimes doctors want to match 8 HLA markers. Other times, doctors want to match 10 markers. These are a few matching rules:

  • Be The Match® requires that patients and donors from the Be The Match Registry® match at least 6 of 8 HLA markers.
  • For a haploidentical (half-matched) transplant, donors match exactly half, or 5 of 10, HLA markers. The donor is usually the patient’s parent or child.
  • A CBU must match at least 4 of 6 markers.

Different transplant centers may have different matching rules. Ask your transplant team what the minimum HLA match is at your center.

"My siblings were not a match so the transplant coordinator began an unrelated donor search. She kept me fully informed the whole time. The search moved quickly but for me it seemed an eternity. My first candidate donor could not participate but the second could. To this day I am amazed and in awe of someone who would donate their stem cells to save the life of a complete stranger."
—Transplant recipient