Human leukocyte antigen (HLA) typing is used to match patients and donor for blood and marrow transplant. HLA are proteins – or markers – found on most cells in the body. The body’s immune system uses these markers to recognize which cells belong to the body and which do not.
A close match between the patient’s HLA markers and the donor’s can reduce the risk that the patient’s body will attack the donor cells or that the donor cells will attack the patient’s cells after the transplant.
A well-matched donor is important to the success of the transplant. There are many HLA markers. The best case scenario is that 10 out of 10 HLA markers will match. These requirements are based on research studies of transplant outcomes.
Other Factors in Determining a Match
To select the best possible donor or if there is more than one donor, the doctor will look at other factors such as the donor’s age, gender, blood type, size, health, number of pregnancies in a female donor or whether the donor tests positive for a common virus called CMV. All of these factors are known to affect the transplant outcome. For example:
If a patient has more than one 10/10 match donor, a male or a female that has never been pregnant is preferred.
If multiple matches are available, the youngest donor will usually be selected after taking into the donor’s health and prior exposure to common viruses.