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Bone marrow transplantation: The ultimate exercise in matchmaking

candy heart - smallStanford Blood Center is home to one of the top human leukocyte antigen (HLA) histocompatibility laboratories in the country. While the center is best known for supplying blood products to hospitals, SBC’s HLA lab supports the success of hundreds of bone marrow transplants administered at Stanford Health Care by providing and developing tests to determine donor and recipient organ compatibility.

What Is Bone Marrow?

Bone marrow is in the center of the bone and contains hematopoietic stem cells (HSC). These cells are immature cells that can grow into red blood cells, white blood cells or platelets, which serve the following purposes in the body:

  • Red blood cells carry oxygen throughout the body
  • White blood cells help fight infections
  • Platelets help control bleeding

When bone marrow is damaged or destroyed, it can no longer make normal blood cells and a stem cell transplant (bone marrow transplant) is required.

Bone Marrow Transplantation

A bone marrow transplant is the process of replacing unhealthy HSC with healthy ones in order to restart hematopoiesis, the process of generating red blood cells, white blood cells, and platelets.

Patients requiring a bone marrow transplant are often being treated for one of the following:

Patients requiring a bone marrow transplant are often being treated for one of the following:

  • Blood cancers like leukemia
  • Diseases which result in bone marrow failure like aplastic anemia
  • Other immune system diseases

In some cases, the patient will receive an autologous transplant where the stem cells come from the patient’s own blood or bone marrow, which would need to have been drawn and stored prior to the patient becoming ill.

When a patient receives stem cells from another person, it's called an allogeneic transplant. When conducting an allogeneic transplant, it's of the utmost importance that the donor and patient’s immune systems are closely matched; otherwise the patient will either reject the healthy donor HSC or the donor cells can attack the patient. The latter scenario is called graft-versus-host disease, and can be fatal in some cases.

The importance of HLA matching

To determine whether a donor and patient’s HSC match well enough for a successful transplant, HLA testing is performed on both the potential donor and patient. Technicians look at a total of five different HLA loci, with two alleles at each locus, giving a total of ten alleles to consider for matching. Nine or more out of ten matches bodes a successful transplant. Siblings are ideal donor candidates because of the likelihood of a 10/10 match. However, even if a sibling is not a perfect match, their HSC may still be used for the transplant, as these mismatches among siblings are better tolerated that a product from an unrelated donor.

If bone marrow from a sibling is unavailable, the lab will search the National Marrow Donor Program registry for a match.

How to become a bone marrow donor

Consider becoming a bone marrow donor and see if your HLA type could be a match for a sick patient. To find out how to become a donor or to learn more about bone marrow transplantation, visit Be the Match.

Kristin Stankus is the digital community & social media specialist at Stanford Blood Center. A version of this entry originally appeared on the blood center’s blog.

Previously: Biomarker can predict graft-versus-host disease in men after transplants from women donors and New issue of Stanford Medicine magazine asks, What do we know about blood?
Image, which has been revised from original, by Maura Teague

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