Stem Cell Transplant: HLA Typing

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Human leukocyte antigen (HLA) typing is a system that finds special markers (antigens) in some white blood cells. These cell markers help the body’s immune system tell the difference between itself and non-self. The immune system fights diseases.

When your child needs a stem cell transplant, we look for a match with the A, B, and DR antigens. Everyone has 2 antigens. We get 5 from our mother and 5 from our father, for a total of 10 antigens. Since these antigens are passed down from parents (inherited), it's more likely that a relative, especially a sibling, is a perfect match (10 out of 10). There's a 25% chance of finding a perfect-matched sibling in a family that has children from the same parents.

an example of HLA Typing 

If there's not a perfect match in your family, we search stem cell registries from all over the world. These registries have HLA data on millions of people who have offered to give stem cells to someone who needs a stem cell transplant.

If we need to search for a match, your child's health care team will give you more information and answer your questions.

How HLA Typing Is Done

HLA typing can also be done 1 of 2 ways:  with a swab kit or a blood draw. Both parents, your child who is sick, and your other children will be tested.

  • Swab Kit – In the kit, there are 4 swabs: 1 for the upper right side of the mouth, 1 for the upper left side of the mouth, 1 for the lower left side of the mouth, and 1 for the lower right side of the mouth.
  • Blood Draw – About 6 teaspoons of blood are taken from a vein in the arm using a small needle. If your child has a central venous line, blood can be taken from the catheter.

About Blood Draws

  • Before getting blood drawn, it’s important to eat.
  • Drink a lot of fluids on the day of the blood draw.
  • Some people feel dizzy or may pass out after their blood is drawn. This is normal.
  • There may be a bruise on the skin where the blood was taken.
  • Early test results will be back in about 7 to 10 days. Final results will be known in about 2 weeks.

If you have any questions, ask your child’s doctor or health care provider.


Stem Cell Transplant: HLA Typing (PDF), Nepali (PDF)

HH-I-213 • ©2002, revised 2023 • Nationwide Children's Hospital