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What is HLA

HLA is the “ID card” on the surface of cells. It is the most important factor when choosing a transplant donor.

Last updated: ~1 min read
HLA markers on a cell surface
Figure 1.HLA markers on a cell surface

01Short answer

HLA (human leukocyte antigens) are proteins on the surface of almost all cells. The immune system uses them to tell “self” from “foreign”. In a stem cell transplant, the closer the HLA match between donor and patient, the lower the risk of rejection and of graft-versus-host disease (GVHD). HLA genes are inherited from parents, so the best match is often a brother or sister. HLA type is found from a blood sample or a cheek swab.

02Simple explanation

HLA is a cell’s “flag”.

Matching flags mean the immune system stays calm.

03Scientific explanation

For transplant, mainly HLA-A, -B, -C and -DRB1 (sometimes -DQB1 and -DPB1) are compared with high-resolution typing, for example an “8/8” or “10/10” match.

In a haploidentical transplant a half-matched relative is used; with special prevention, results are good in many cases.

04What happens in the body?

Why it matters

If HLA does not match, the donor’s immune cells can attack the patient’s tissues (GVHD) or the patient’s immunity can reject the graft.

How a donor is found

Brothers and sisters are typed first. Then national and international registries are searched. Sometimes a half-matched relative (a parent or child) or cord blood is chosen.

A match like keys
Figure 2.A match like keys — What is HLA

Good to know

Blood group is not the same as HLA: after a transplant your blood group may change to the donor’s. This is normal.

A network of donor registries
Figure 3.A network of donor registries

05Donor matching

Four steps.

Typing — A blood sample or cheek swab.1TypingA blood sample or cheek swab.
Comparison — HLA markers are compared.2ComparisonHLA markers are compared.
Relatives first — Siblings are checked.3Relatives firstSiblings are checked.
Registry search — Donors worldwide.4Registry searchDonors worldwide.
Less riskA good match lowers complications.
More optionsHalf-matched donors widen the choice.

06Key points at a glance

TopicIn brief
Why it mattersIf HLA does not match, the donor’s immune cells can attack the patient’s tissues (GVHD) or the patient’s immunity can reject the graft.
How a donor is foundBrothers and sisters are typed first. Then national and international registries are searched. Sometimes a half-matched relative (a parent or child) or cord blood is chosen.
Good to knowBlood group is not the same as HLA: after a transplant your blood group may change to the donor’s. This is normal.

07Key terms

HLA
Human leukocyte antigens, a cell’s identity.
Haploidentical
A half-matched related donor.
Registry
A database of volunteer donors.

08Key points

  • HLA is the immune “ID card”.
  • A match lowers transplant risk.
  • Siblings are checked first.
  • Half-matched donors are possible too.

09Frequently asked questions

Can a donor have a different blood group?

Yes, HLA matters more; blood group differences are managed.

Is donating painful?

Most often cells are collected from the blood; sometimes from the marrow under anaesthetic.

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. Can a donor have a different blood group?

  2. Is donating painful?

My questions

12Sources

  1. MedlinePlus (U.S. National Library of Medicine). Histocompatibility antigen test
  2. National Cancer Institute (NCI). Stem Cell and Bone Marrow Transplants for Cancer
  3. Anthony Nolan. Understanding stem cell transplants
  4. NHS. Stem cell and bone marrow transplants
  5. Cancer.Net (ASCO). Talking With Family and Friends
  6. NHS. High temperature (fever) in adults
  7. NHS. How to wash your hands
  8. MedlinePlus (U.S. National Library of Medicine). Peripherally inserted central catheter - dressing change
  9. Cancer Research UK. Coping emotionally with cancer
  10. National Cancer Institute (NCI). When Someone You Love Is Being Treated for Cancer (booklet)
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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