Bone marrow matching identifies a compatible donor for individuals needing a stem cell or bone marrow transplant. These transplants treat various serious conditions, including certain cancers like leukemia and lymphoma, and blood disorders such as sickle cell anemia. Finding a suitable match is crucial for transplant success and minimizing complications. Donor-recipient compatibility impacts patient recovery and long-term health.
The Importance of Genetic Markers
Bone marrow matching relies on the Human Leukocyte Antigen (HLA) system. HLA markers are proteins on cell surfaces that the immune system uses to distinguish between the body’s own cells and foreign invaders. Class I (HLA-A, HLA-B, HLA-C) and Class II (HLA-DR, HLA-DQ, HLA-DP) genes are important in transplantation. These genes are highly diverse, meaning many different variations exist within the human population.
A close HLA match between the donor and recipient prevents the recipient’s immune system from recognizing transplanted cells as foreign and attacking them, known as rejection. Without a close match, donor immune cells might attack the recipient’s body, leading to a complication called Graft-versus-Host Disease (GVHD). Precise HLA typing is performed to find the most compatible donor, enhancing transplant success and reducing these risks.
The Testing Process
Bone marrow compatibility testing starts with collecting a sample from the potential donor. This involves a simple cheek swab, where cells are collected from the inside of the mouth using a cotton swab. Alternatively, a blood sample can be drawn. Both methods provide DNA for analysis.
Once collected, samples are sent to a laboratory for DNA analysis to identify specific HLA markers. HLA typing determines the immune system’s unique genetic profile. Advanced techniques, such as next-generation sequencing, are used for high-resolution results, identifying minor HLA gene variations. This information is then added to a registry for comparison with patient profiles.
Interpreting Match Results
A “perfect” match in bone marrow transplantation is a 10/10 HLA match, where all ten key HLA markers are identical between the donor and recipient. Some systems may refer to an 8/8 match, focusing on four pairs of HLA markers. While a perfect match is ideal for minimizing rejection and GVHD, it is not always feasible to find one.
When a perfect match is unavailable, a “haploidentical” match is an option. A haploidentical donor shares exactly half of their HLA markers with the patient, often an immediate family member (e.g., parent, child, sibling). Advances have made haploidentical transplants a viable alternative, expanding the donor pool. Though they may carry higher risks, they offer a life-saving option for many patients.
Registering as a Potential Donor
Individuals interested in becoming a bone marrow donor can register with national or international registries (e.g., Be The Match in the U.S.). The process involves completing a registration form and providing a cheek swab or blood sample for HLA typing. Eligibility typically includes being 18-40 years old and meeting general health guidelines, though some registries accept donors up to age 60. Younger donors are preferred for better patient outcomes.
Once registered, a potential donor’s HLA type is added to the database, making them globally available. Donors must keep their contact information updated and inform the registry of any significant health changes. If identified as a potential match, the registry will contact the donor, and further health screenings and confirmatory tests are performed.