Role of HLA Matching Basics

A close HLA match improves the chances for a successful transplant. Close matching:

  • Promotes engraftment. Engraftment is when the donated cells start to grow and make new blood cells. 
  • Reduces the risk of a post-transplant complication called graft-versus-host disease (GVHD). GVHD occurs when the immune cells from the donated marrow or cord blood (the graft) attack your body (the host).

What is HLA typing?

HLA refers to proteins found on almost all cells of the body. These proteins are called human leukocyte antigens (HLA) because they were originally identified on white blood cells. HLA typing is used to match patients and donors for marrow and blood cell transplants. HLA matching plays an important role in engraftment, incidence of graft-versus-host disease (GVHD) and overall survival. The first step is to identify your HLA antigens at a high resolution. You would be tested for the HLA Class I antigens HLA-A, -B and -C and for the Class II antigen HLA-DR.

Your full biological siblings should be typed to identify potential related donors. In addition, for some people, typing their parents and/or children can provide additional information that can be useful in developing a successful donor search strategy. HLA expertise (available at many transplant centers and from the NMDP) is critical to ensure potential donors in the person’s family are not overlooked. To save time, typing the family and submitting a preliminary search to the NMDP for an unrelated donor or cord blood unit can be done at the same time. HLA-identical siblings are the preferred donors. However, approximately 70% of people in need of a transplant do not have a suitable sibling donor. Initiating an unrelated donor search early in the course of investigating treatment options allows time for more challenging searches and improves the likelihood that a transplant can be performed at the time when it has the best chance to succeed.

HLA expertise is available at many transplant centers and from the NMDP. To request an HLA consultation from the NMDP, contact the NMDP Office of Patient Advocacy at 888.999.6743 (toll-free in the United States) or 612.627.8140 or by e-mail at