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Medical glossary

HLA: human leukocyte antigens

HLA are proteins on the surface of cells that help the immune system tell “self” from “foreign”. They are the main measure used to choose a transplant donor.

Last updated: ~1 min read
A ribbon model of an HLA class I molecule holding a small peptide
Figure 1.An HLA molecule displays a small protein fragment on the cell surface

01Short answer

HLA genes sit on chromosome 6 and are very varied; everyone inherits half from their mother and half from their father. So the chance that a brother or sister is a full match is about one in four. HLA typing is done from blood or a cheek swab. The better the match, the lower the risk of GVHD and rejection, but newer methods have also made half-matched donors possible.

02Simple explanation

Surface markers.

Self and foreign.

Donor choice.

Half from each parent.

03Scientific explanation

NCI: HLA are proteins on the surface of almost all cells in the body and are used for tissue matching.

The NCI Dictionary explains cancer terms in plain language; check the exact meaning for your situation with your doctor.

04What happens in the body?

How it is tested

Blood or a cheek swab.

Comparing
Figure 2.Comparing — HLA: human leukocyte antigens

Who might match

Brothers, sisters, parents or a registry donor.

Family
Figure 3.Family — HLA: human leukocyte antigens

Where you will see this word

In test results, discharge letters and conversations with your doctor. Write the word down and ask what it means.

Ask your doctor

The general meaning and the meaning of your own result can differ. The most important question is “What does this mean for me?”

05From an unfamiliar word to a clear answer: four steps

Write it down, look it up, prepare a question, ask.

Write it down — From a result or a conversation.1Write it downFrom a result or a conversation.
Look it up — Learn the plain meaning.2Look it upLearn the plain meaning.
Prepare a question — What does this mean for me?3Prepare a questionWhat does this mean for me?
Ask — Your doctor gives the personal explanation.4AskYour doctor gives the personal explanation.
UnderstandingResults feel less frightening.
ConversationA shared language with your doctor.
SafetyNot drawing conclusions alone.

06Key points at a glance

TopicIn brief
How it is testedBlood or a cheek swab.
Who might matchBrothers, sisters, parents or a registry donor.
Where you will see this wordIn test results, discharge letters and conversations with your doctor. Write the word down and ask what it means.
Ask your doctorThe general meaning and the meaning of your own result can differ. The most important question is “What does this mean for me?”

07Key terms

HLA typing
A tissue-matching test.
Haploidentical
Half-matched.
Term
A word with a precise medical meaning.
Reference range
The range a laboratory considers normal.

08Key points

  • Learn.
  • Ask your doctor.
  • Write it down.
  • Write the word down.
  • Ask what it means.

09Frequently asked questions

Is HLA the same as blood group?

No, they are different systems.

What if there is no full match?

There are other options; the team will explain.

This word is in my results: should I worry?

The word itself does not mean a serious or mild condition; get the explanation from your doctor.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. Is HLA the same as blood group?

  2. What if there is no full match?

  3. This word is in my results: should I worry?

My questions

12Sources

  1. National Cancer Institute. NCI Dictionary of Cancer Terms: human leukocyte antigen
  2. National Cancer Institute. Stem Cell and Bone Marrow Transplants for Cancer
  3. NMDP (Be The Match). About transplant
  4. National Cancer Institute. NCI Dictionary of Cancer Terms
  5. National Cancer Institute. Leukemia
  6. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: neutrophil
  7. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: neutropenia
  8. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: bone marrow biopsy
  9. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: karyotype
  10. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: port
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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