HLA typing is a test that identifies a person’s human leukocyte antigens (HLAs). HLAs are protein markers on the surface of cells in the body. The markers act like “flags,” which tell the immune system if cells are a normal part of the body.
Each person has a different combination of HLA markers. They are determined by genes, which are inherited, or passed down from parents to children. So, family members may have similar HLA types. Since children inherit one set of HLA markers from each parent, parents are always a half match to their children.
HLA typing is an important first step of testing before an allogeneic stem cell (bone marrow) transplant. HLA typing may also be done before organ or other tissue donations.
The HLA type of your child should match that of the donor as much as possible. If the donor cells are not well-matched to your child's HLA type, your child's cells and the donor cells may attack each other.
Some HLA types are hard to match because they are rarer.
HLA typing helps match donors with transplant recipients.
A good HLA match helps the body accept the donor cells. If the body’s immune system detects cells with a different HLA type, the body might attack and reject the donor cells (graft rejection).
HLA matching also decreases the chance of a complication called graft versus host disease (GVHD). GVHD occurs when donor cells (the graft) see the patient’s cells and tissues (the host) as foreign and attack them.
HLA matching improves the chances for a successful transplant with fewer complications.
There is no special preparation that you need to do for HLA typing. HLA typing is done at clinics, transplant centers, and cancer centers. Your child and potential donors will be tested. HLA typing can be done from a blood sample or a cheek (buccal) swab. The lab looks at the DNA from the cells in the sample to find the HLA type.
Blood sample
A health care provider will take a blood sample using a needle stick into a vein (venipuncture).
Cheek (buccal) swab
Your care team may also use a cheek (buccal) sample to find the HLA type. A health care provider will use a swab to take a sample of skin cells from inside the mouth, near the cheek. The swab is placed in a special tube and sent for analysis by the lab.
In some cases, home kits can be used for testing. You will be given instructions about how to do the cheek swab at home by your health care provider.
There are few risks of HLA testing. Taking a blood sample may cause:
- Bleeding, bruising, and soreness near the blood draw site
- Infection at the site of the blood draw
- Feeling light-headed or faint
The cheek swab may cause slight irritation inside the mouth.
It may take several weeks to get the results.
Finding a good match for a transplant may be challenging. There are many HLA types.
Your care team may ask that family members be tested to see if they are a good match for your child. This could include biological parents, full siblings, and half-siblings. Donors must be a good match, willing to donate, and able to travel if needed.
If no relatives are a good match, the donor cells may come from a volunteer donor who is well matched. Unrelated donors are sometimes found through NMDP (formerly known as the National Marrow Donor Program and Be the Match).
There are 3 different types of matches for a transplant:
- Full match: The patient and the donor have the same HLA markers. This is the best match, but it can be hard to find.
- Partial match (mismatched): The donor matches most, but not all, of the patient’s HLA markers.
- Haploidentical match (half match): If the patient and the donor share half of the same HLA markers, this is a haploidentical or “haplo” match. Parents are always a half match for their child.
The better the match, the higher the chance for a successful transplant and the lower the risk of complications. With advances in transplant methods, mismatched donor transplants are fairly common, and many are successful.
Several factors can increase the likelihood of finding a good HLA match for a transplant:
- Siblings with the same biological parents: Full brothers and sisters have the highest chance (about 1 in 4) of being a full HLA match because they inherit HLA markers from both parents.
- Similar ethnic background: People are more likely to find a match with someone from the same ethnic or racial background. HLA types are inherited and can be more common in certain groups.
- Large family size: Having more siblings or close relatives increases the chances of finding a match within the family.
- Participation in donor registries: The more people who register as donors—especially from diverse backgrounds—the higher the chance of finding a match for patients who need a transplant.
Your care team will talk to you about HLA testing and who in your family should be tested. They will help you understand HLA matching and discuss donor options with you. If you have questions about HLA matching or finding a donor, your care team can help explain your options.
Questions to ask your care team
