What is HLA?

HLA stands for human leukocyte antigens. HLA are proteins—or markers—on most cells in your body. Your immune system uses HLA to see which cells belong in your body and which do not. You have many HLA markers. To match patients and donors or cord blood units for blood stem cell transplants, doctors use HLA typing to look at specific HLA markers. HLA matching is much more complicated than blood typing.

The first step is to have your blood drawn or the inside of your cheek swabbed. Your doctor will send the blood sample or cheek swab to lab where it’s tested to figure out your HLA type.

Your doctor may ask some of your family members to get HLA typed, too, using a cheek swab or blood draw. Your doctor might also search the NMDP Registry^SM for an unrelated donor or cord blood unit. Your HLA type will be compared to potential donors and cord blood units to see if there is a match.

Sometimes a patient and donor or cord blood unit will share all the same HLA markers. That’s considered a full match. With advances in transplant, it’s also possible for some patients to safely have a transplant using a donor that matches most, but not all, of their HLA. You might hear this called a partial match. For other patients, a haploidentical (haplo) transplant is the best option. That’s when the patient and donor share half of the same HLA.

Your doctor will use detailed testing to decide which donor is the best HLA match for you.

HLA is inherited so you are most likely to match a sibling or an unrelated donor of a similar ethnic background. Sometimes it’s hard to find a fully matched donor because some HLA types are less common.

In your family, each brother and sister who shares the same parents as you has a 25% chance (1 in 4) of being a complete (or full) HLA match. About 70% (7 out of 10) of patients who need a transplant won’t have a fully matched donor in their immediate family. Extended family members are not likely to be full HLA matches.

Because you inherit half of your HLA from your mother and half from your father, parents and children share half of the same HLA. So your parent or child could be your donor for a haploidentical transplant.

You can have HLA typing done at your:

• Transplant center
• Cancer clinic or cancer center

HLA typing should be done early after your diagnosis. If you haven't been to a transplant center yet, your doctor can have your HLA typing done for free through our NMDP^SM HLA Today program.

Contact our Patient Support Center with any questions:

• Call or text: 1 (888) 999-6743
• Email: patientinfo@nmdp.org

If you are a hematologist or oncologist who would like to learn more about our HLA Today program, visit network.nmdp.org (Opens in a new tab) or email us at HLAToday@nmdp.org.

Your doctor wants to find the best possible donor or cord blood unit (CBU) match for you 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).

Your best match could be a full match, partial match or half match (haploidentical). There are factors beyond HLA that also help your doctor decide on the best donor or cord blood unit for you. Talk to your transplant team if you have any questions about HLA matching or how they’ll choose a donor.