The Science of a Perfect Match
When you join the registry, you have the potential to save a life; however, how exactly does Be The Match figure out who your perfect match is? In this week’s blog post, we are going to be talking about the basics of HLA typing, where your swab kit goes after donation, and what happens when a donation is rejected by the patient.
What Is HLA typing?
HLA stands for Human Leukocyte Antigen, and is a surface molecule found on all cells with a nucleus. In other words it is a particle that is on the outside of all of the cells in your bloodstream besides your red blood cells. This set of antigens/surface markers is unique to you, as you inherit half from each parent. This means that your specific set of antigens comes from your genetics, or the code in your DNA. In the case of the registry, HLA markers are used to identify how close of a match you are to a patient in need to donate stem cells, however, these antigens can be used for many other purposes, such as finding an organ donor and identifying different diseases. With HLA markers, there are two classes of them: HLA Class I and HLA Class II. Both classes are used when finding a match.
Where does your swab kit go after registration?
Once you swab to join the registry, your envelope with your unique code and swab is sent to a lab. At this lab, your HLA profile is determined through a series of tests. After this, your HLA profile (your specific group of antigens) is put into a Be The Match Database. Doctors around the world can then search this database to find a match for their patients. The similarity of your HLA profile to the patient’s HLA profile is what determines if you are a match for them. This is measured on a scale of 1-10, with 1 being that you and patient share no genetic material, and 8-10 being that you and the patient share enough genetic material to be a match. Since your HLA profile is determined by your DNA, if you share a similar HLA profile with someone, you also share similar DNA. This is why you are much more likely to match someone who is of your ethnicity, as you share similar DNA.
What happens if the donation is rejected?
Sometimes, when a patient is not able to find a good HLA match, usually 8-10 on the scale, their doctor must make the decision of whether or not to opt for a donation from someone who isn’t as perfect of a match. This means weighing the risk of possible GVH syndrome. Graft Versus Host is a condition that occurs when the stem cell donation is rejected by the patient’s body, and can often lead to painful symptoms—some even worse than the ones caused by the condition which caused them to need a donation. This is why it is so important that we fix the ethnic disparities in the donation registry so that all patients can find their life-saving match, regardless of ethnicity.
Be on the lookout for our next blog post on September 19!
