How Donors Are Selected

When you took the first step to become a bone marrow donor by joining the Be The Match Registry^SM, you were told patients are searching for a match.

But what exactly is being matched?

The short answer: HLA. Human leukocyte antigens (HLA) are proteins — or markers — found on most cells in your body. Your immune system uses these markers to recognize which cells belong in your body and which do not. A close HLA match between patient and donor is the most important factor in selecting the best bone marrow donor for a patient.

A close match

There are many HLA markers, but matching only a small number of them is critical to a successful transplant.

We test most new members for 6 HLA markers when they join the Be The Match Registry. By testing for a basic level of HLA markers, we keep tissue-typing costs low — we want to be able to add as many registry members as possible to help all searching patients find a matching donor.

Next step

A patient’s doctor usually tries to select several potential donors who appear to match the patient at a basic level. The doctor then asks for additional testing to find a donor who matches the patient at a detailed level. (For more information, see When You're Contacted as a Possible Match.)

Other factors

If more than one potential donor is a good HLA match for a patient, doctors will also consider other factors, such as the donor’s age, gender and size.

When you’re selected

To learn what happens if you are selected as the best donor for a patient, see When You’re Asked to Donate for a Patient.