Human Leukocyte Antigen (HLA) typing is a testing process that is used to match patients and donors for cord blood or bone marrow transplants.
HLA antigens are proteins found in most cells in our body. Our immune system uses these proteins or markers to recognize which cells belong in our body and which do not. If the immune system determines a cell as not belonging to the body, the cell is attacked. Thus, HLA typing is done to reduce the risk of the transplanted stem cell being attacked by the immune system of the recipient. A close match between the patient's HLA antigens and the donor's can reduce the risk of the patient's immune cells attacking the donor's cells or vice versa. HLA typing is usually done for all allogeneic transplants, using a blood sample.
HLA Typing For Stem Cell Transplants
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A well-matched donor is important to the success of the stem cell transplant. There are 6 HLA markers that are matched. For a successful transplant, at least 4 of these 6 markers must match. In some cases even a 3/6 match has been successful. However, it is best to have 4 or more markers that match as it reduces the risk of graft versus host disease. As HLA antigens are inherited, the best chances of finding matches are between siblings. As everybody inherits half of their HLA antigens from their mother and half from their father, a sibling has a 25% chance of matching another. During a transplant, the patient's parents and/or children are also tested to confirm the HLA typing and to make sure no possible donors are overlooked. |
| Relationship |
Chances of matching |
| Sibling - sibling |
25% |
| Parent - child |
50% |
| Cousins |
6.25% |
The Advantages of HLA Typing
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HLA Typing improves the chances of a successful transplant. Matching HLA tissue traits before a transplant is mandatory, as it: |
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Promotes Engraftment - Engraftment occurs when the donated cells that were transplanted begin to grow and make new cells. For the transplant to succeed, the donated cells need to engraft quickly, as the patient is at a high risk of infection. |
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Reduces the risk of Graft-Versus-Host Disease (GVHD) - A post-transplant complication, GVHD occurs when the immune cells from the cord blood (the graft) attack the patient's own immune cells. |