Finding a Matching Donor
The first step in finding a matching donor is to determine the patient's tissue type, so that the search can be started. This means a prompt visit to a transplant center, plus starting the tissue typing search among blood relatives, in case one of them is a match. Starting an unrelated donor search in the public registries right away can also save time, and can be done by Gift of Life or by a transplant center.
What are HLAs and what is tissue typing?
The important factor in tissue type is the Human Leukocyte Antigen (HLA), which is a complex of genes in every person's DNA that regulates the immune system. They are also responsible for whether a transplant is accepted or rejected by the body, so a good match is crucial. Tissue typing is the laboratory process where a tissue sample collected from inside the patient's cheek on a cotton swab (or possibly via a blood draw) is analyzed to determine the HLA types. Ten HLA factors are determined, and once the HLAs for a patient are known, the search for a matching donor can be started.
To read an overview about HLAs and how they affect tissue typing and matches, click here.
Family members as potential donors
Since HLA are a genetic factor inherited from parents, it is logical to turn first to family members and test for a match. However, because the genes we inherit are a combination from our parents, only 30 percent of those seeking a transplant match find a donor within their own family. Those who don’t find a match within the family (70 percent of patients do not find one) can search the worldwide marrow donor registries to find a match.
Searching the worldwide registry, including Gift of Life's registry
The worldwide registries, including Gift of Life Marrow Registry, are made up of volunteer donors who offer to become bone marrow or blood stem cell donors in the event they are determined to be an HLA match with the recipient. Searches are done through a central database called Bone Marrow Donors Worldwide, which links to registries around the world that hold the tissue type information of over 34 million volunteer donors. That sounds like a large number, yet the world population is 7.7 billion, so volunteer donors comprise 0.44 percent of the world population, less than one-half of one percent.
Finding a perfect match
Perfect matches can be found in the registry, even though the donor and recipient are not siblings. When two people share an ethnic background, there is a chance that their HLAs will match up and the donation can take place.
The importance of diversity in the registry
Ethnicity and ancestry play a big role in the ability to find a match – some ethnic groups are underrepresented in the registries, making it difficult for some people in need to find their match. Building the diversity of the registries is a mission of Gift of Life – adding diversity to the registry will result in more life-saving matches for those in dire need.
What is a haploidentical transplant?
If a perfect HLA match is not available, a haploidentical transplant is often recommended. This means the donor is a half-match for the recipient. Parents are always at least a half-match for their children, and siblings have a 50 percent chance of being a half-match for each other, and a 25 percent chance of being a perfect match.
What is an umbilical cord blood transplant?
Cord blood is simply collected after a baby’s birth. It is packaged and shipped to a repository where it is tested and processed, then frozen in liquid nitrogen. If a patient’s tissue type matches that of a cord blood unit, it is sent to the patient’s hospital for a transplant. Because cord blood stem cells are immature, a perfect match is not necessary.
What if no match is found in the registry?
If no match is found in the worldwide registry, that doesn’t mean no match exists, but that no one who is a match has yet registered as a donor. The family and friends of a patient can start a donor recruitment drive to try and find a match among the new donors they sign up. Gift of Life provides support for patients and their families in organizing, publicizing and running donor drives, including the online tool called Donor Circles, a way to create a central hub for a recruitment drive, with tools for live tracking of results, including matches and transplants that come from among a circle’s sponsored donors.
Continue to next section, The Donation Process.