Frequently Asked Questions
What is HLA?HLA stands for Human Leukocyte Antigen
Why is HLA so important?Human Leukocyte Antigens are protein molecules that we inherit from our parents. Thousands of different HLA molecules have been identified, and matching essential HLA types is critical to the potential success of an HSCT.
In HSCTs, it is important to determine how closely the HLA type of the patient matches the HLA type of the donor. The HLA "match" is the number of HLA molecules that any two people have in common. HLA matching is usually based on ten HLA molecules. The more molecules two people share, the better the match. That is, their immune systems are less likely to see each other as "foreign" and are therefore also less likely to attack each other.
The most likely place to find an HLA match between two people is among siblings (that is, a brother or sister who share the same parents). If siblings inherit the same HLA molecules from both parents as the patient, they are said to be an "HLA identical match."
There is a 25% or one in four chance of being an identical match with a sibling. If no sibling match is found, doctors will frequently ask addiditional blood-related family members to be tested. These are usually aunts, uncles, cousins and grandparents.
However, two unrelated people can also be a good HLA match. Although it is less likely, it is possible that you could have some of the same HLA molecules as a friend or someone you don't even know. If you and the patient share three HLA molecules, for example, then you are said to be a "three HLA antigen match."
Why is it important to have a specific donor "match"?Because stem cells are specific to certain aspects of the individual's genetic make-up, transplants must be matched to the patient's HLA type to minimize any immunologic reactions. This laboratory analysis is also referred to as "tissue typing." The better the match on HLA parameters, the higher the likelihood of a successful transplant for the patient. Regardless of race or ethnicity, each person has a unique tissue type inherited from his or her parents, which is why the chances of finding a match are best among family members. This is why physicians first look for a match within the patient's immediate family.
How are the marrow or stem cells given to the patient?The patient's marrow is first treated with Chemotherapy and/or radiation to wipe out diseased cells, and then he or she receives the new healthy stem cells through an IV transfusion similar to a blood transfusion. The stem cells travel through the patient's bloodstream to the marrow spaces, where they begin to grow and provide healthy new blood cells. It takes about a month for the first signs of Engraftment to be evident, meaning that the transplant has begun to work and is producing new healthy cells. During this time the patient is vulnerable to infection and usually remains hospitalized.
What are the risks to the patient?Not all patients survive the pre-transplant procedures of Chemotherapy and radiation. In addition, other patient complications including non-Engraftment, rejection, graft-versus-host disease (the donated stem cells cause an immune reaction attacking the patient's body), infection and relapse of the original condition. However, thousands of patients receiving stem cell transplants do recover and go on to lead healthy, productive lives.
The information presented in these FAQs is not meant to be, nor should be taken as, medical advice. Kashi Clinical Laboratories strongly encourages you to consult a qualified physician before using the information, products and services available on this website.