Human leukocyte antigen (HLA) typing is a way to tell how closely the tissues of one person match the tissues of another person. It is important in bone marrow and stem cell transplants to know how closely the transplant recipient matches their donor.
We can determine your HLA type and a potential donor’s type by taking a sample of blood or another body tissue.
What is an HLA match?
Human leukocyte antigens are proteins you inherit from your parents. Together, your HLA proteins, or markers, make up your HLA type. Your immune system uses HLA markers to recognize which cells belong in your body and which do not.
An HLA match is the number of HLA markers that any two people have in common.
- HLA matching is usually based on either eight or 10 HLA markers.
- The more markers two people share, the better the match.
- A good match means their immune systems will not see each other as foreign and are less likely to attack each other.
Who is likely to be an HLA match?
The most likely place to find an HLA match is among siblings who have the same mother and father.
- You have a 25-percent chance of inheriting the same HLA markers as your sibling (an HLA-identical match).
- You have a 50-percent chance of inheriting half of the same HLA markers as your sibling (a haploidentical match).
- You have a 25-percent chance of inheriting none of the HLA markers your sibling inherited.
Two unrelated people can just happen to be a good HLA match, too, although it is less likely.
How do we find the best HLA match?
When a doctor recommends a bone marrow transplant, the patient, their siblings and sometimes their parents will have samples (a blood draw or a swab of the inside of the cheek) collected for HLA typing. These will be tested in a lab. It usually takes about one to two weeks to get the results of typing.
- If a relative is an identical match, the lab will do further testing to be absolutely sure that they are the best match possible.
- If no sibling is a good match, the doctor may ask to test other family members. Your parents and children have the next best chance of being closely matched with you.
- If there are no close matches within the family, the health care team will contact the National Marrow Donor Program to search international registries for an unrelated volunteer donor who is a match.
- If you haven’t found a suitable match, you may be able to have a minimally mismatched, haploidentical or cord blood transplant at Seattle Cancer Care Alliance (SCCA). Learn more about these new options for people seeking a donor match.
Request HLA Typing at SCCA
At SCCA, we typically receive requests for HLA typing from treating doctors — for example, your primary oncologist. Though we can talk about HLA typing directly with you, we recommend that your doctor be involved.
When we receive your request, the SCCA intake department will work with your doctor to determine three things:
- What is the clinical urgency, based on your condition?
- What is your treatment plan?
- Are you considering searching for an unrelated donor if there is no family match?
Next, we will:
- Contact you to explain the HLA typing process and collect information about your insurance and your family member who is willing to donate.
- Contact your insurance carrier for financial clearance.
- Communicate with you about any financial implications of HLA typing.
If we need to discuss changing the HLA-typing strategy based on any of the information collected, one of our doctors will contact your local doctor or you.
Our Clinical Immunogenetics Laboratory will send instructions to your local doctor about how to collect and send samples for HLA typing.