BM Transplant down arrow

Home > Disclaimer > Bone Marrow Transplant


Bone Marrow Transplant


Allogeneic Hematopoietic Stem Cell Donor

Choosing a donor

HLA Typing  

Potential recipients of a HSCT will have HLA typing done before a donor search is initiated.

HLA typing is now done on peripheral blood samples using highly sensitive high-resolution DNA typing techniques.

This produces a HLA typing for each patient that looks something like this:













The first two numbers refer to the HLA-antigen and the last two numbers refer to the HLA-allele.

HLA-allele level typing is now accepted as the gold standard for HLA-typing and is used to match recipients to donors (exceptions may include umbilical cord transplants).

In most transplants a patient’s siblings and parents are also HLA typed.  First preference is usually given to a fully HLA-allele level matched sibling.  Each sibling has a 25% chance of being a perfect match to the person who needs a transplant (since there is a 50% chance that sibling will have received the same haplotype from mom and 50% chance of receiving the same haplotype from dad.  0.50 multiplied by 0.50 = 0.25).

Only rarely is a parent a perfect HLA match with their children.  This is because they have given only one haplotype to their offspring.  Most often, they are only 50% HLA similar to their offspring. 


Parental haploidentical mismatched HSCT

  • Possible to transplant from a 50% matched parent (parental haploidentical mismatched HSCT), but high risk.
  • Only rarely performed due to concerns about:
    • Severe GVHD
    • Graft rejection
    • Poor immune reconstitution following transplant. 
  • On rare occasion, because of random crossover events during miosis or because certain haplotypes tend to cluster in particular ethnic groups, a parent will be a perfect match for their child (around 2% of the time).  In these situations using a parent as the donor may be possible.


Back to top