A donor's and a recipient's HLA types should match as closely as possible to prevent the recipient's immune system from attacking the donor's marrow as a foreign material that does not belong in the body.
The closer the HLA match between a bone marrow donor and recipient, the lower the chances that the recipient's body will reject the transplanted tissue.
Human Leukeocytic Antigens (HLA) molecules are found on the surface of human white blood cells and help to coordinate the immune response.
They will be tissue-typed to determine whether their bone marrow has the same human leukocyte antigens (HLA) as the affected child.
In addition to siblings, another choice is bone marrow from one of the parents, who shares half the affected child's HLA antigens.