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HLA Matching for Hematopoietic Cell TransplantationThe outcomes of related and unrelated donor hematopoietic cell transplants are strongly affected by the degree of human leukocyte antigen (HLA) matching between the transplant recipient and the donor or cord blood unit. HLA matching plays an important role in engraftment, incidence and severity of graft-versus-host disease (GVHD) and overall survival. In cord blood transplantation, however, several studies have shown that although degree of HLA match is important, a large cell dose is equally important, if not more so. [1-4] Key factors contributing to the efficient selection of a closely matched donor are:
On this page:Tissue typing the patient and familyThe first step in developing an effective donor search strategy is tissue typing the patient using DNA-based testing to identify the patient's HLA antigens at a high resolution (results reported at 4 digits). Current data show significantly better post-transplant survival rates when patients and unrelated donors are matched at a high resolution. [5,6] Beginning with high-resolution patient typing enables a transplant center to select the best-matched donor and can reduce total search time and costs because the search strategy is based on complete information.The patient should be tested at high resolution for the following HLA antigens:
It may also be useful to identify DRB3, DRB4, and DRB5, although the benefit of matching at these loci has not been evaluated. [7] A 2007 study of 3,857 unrelated donor transplants found that mismatches at HLA-DQ or HLA-DP did not affect survival. [6] The patient's immediate family (siblings, parents and children) should be tested along with the patient to:
Patient haplotypes and search strategies The set of alleles inherited from each parent forms a haplotype, in which some alleles tend to be associated together. Identifying a patient's haplotypes can help predict the probability of finding matching donors and assist in developing a search strategy, because some alleles and haplotypes are more common than others and they are distributed at different frequencies in different racial and ethnic groups. When searching for a donor, for some alleles, an allele-level match is more likely to be found among persons of a particular ethnicity. [7] The NMDP has developed HapLogicSM, a new matching algorithm based on these principles, that identifies the donors or cord blood units with the highest potential to match the patient. This allows transplant physicians searching the NMDP Registry to identify more quickly and efficiently the best immunogenetically matched donor or cord blood unit for their patients.  Matching unrelated donors or cord blood units to patientsThe transplant center is responsible for selecting an unrelated donor or cord blood unit for a patient. The National Marrow Donor Program (NMDP) recommends that when possible, patients and unrelated donors should be matched at high resolution (4 digits) for HLA-A, -B, -C, and -DRB1. [7] This does not imply that availability of an only partially matched donor is a contraindication to transplant. Instead, a less-than-optimal match is another risk factor to be considered in developing the patient's treatment plan. [5,7,8]
Request a free preliminary searchAny physician can request a preliminary search to find out about potential marrow or PBSC donors or cord blood units on the NMDP Registry. This preliminary search is free. Results of a preliminary search are available to the requesting physician the next business day after the NMDP receives the request. Early preliminary searches can indicate how challenging the patient's search for a donor may be and help in shaping the patient's treatment plan.Effective search strategiesA preliminary search is a single "snapshot" of potential matches at a given time and does not include contact with or additional testing of a potential donor. To interpret preliminary search results and determine an effective search strategy, it is important to work with a knowledgeable HLA expert, either at a transplant center HLA laboratory or the NMDP.
To contact an HLA expert at the National Marrow Donor Program, call the NMDP's Office of Patient Advocacy at (888) 999-6743 (toll-free in the United States) or at (612) 627-8140.
For more information about the search process, see Searching for an Unrelated Donor or Cord Blood Unit. HLA resources for your patientsThe Patient Resources section of this Web site provides resources to help your patients understand HLA matching and the search process:Using MatchView, patients enter their HLA type to see the number of potential donors and cord blood units they may have on the NMDP Registry. Patients are encouraged to bring their results to their physician as a resource to discuss transplant as a treatment option. Note: MatchView is not an alternative to a donor search conducted by a physician. For more information, see MatchView Physician Information. References
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