What is the HLA score? When are the cutoffs?

What is the HLA score? When are the cutoffs?

So the matching system is, so the HLA system is called the human leukocyte antigen system. That is a portion of chromosome six, which has genes that determine your ability to fight infection, for example, and detect foreign proteins that get into the body. This system basically also tells your cells how to reject donor cells coming in and how to tolerate other people's organs, for example, bone marrow or kidney from another person. So that system is very important in choosing a donor. We basically look at the HLA system as a long system. If you can think of a tape measure, it's like a long stretch of DNA. And basically, we look at eight points at you have to at least look at eight points to call it a modern way of looking at it with what we call a high-resolution HLA typing, which means on these eight points, we are looking at the specific sequence of DNA and those eight points, and four of these points are going to come from your mother and four of these points are going to come from your dad. So basically, the eight points are we call them A, B, C, and D are B one. And if you have all of the full match from a sibling, usually we'll be matched eight out of eight, which means all eight points match closely with the recipient and the donor. And then you assume that intervening points are also going to be mostly matched and you're happy to go forward. Some centers do ten points because they do add one more point, one more point means one from the dad, one from the mother. So now it becomes ten out of ten. You can even do 12. It doesn't generally change if you are looking at siblings. It is basically the same. You do eight or ten or 12. It's most of the time it's the same. Very rarely, you can have a one antigen mismatch in a sibling and it really doesn't matter. We would still go with that. When we look at unrelated donors, again, we look at these eight points, and if you're matched on those eight points, we say that they are almost as good as a sibling because the modern HLA matching picks out that. When we look at half-matched donors, if you, you know, again, so if you are a child of the patient, you would have inherited half his genes and the HLA region would also be the one that you got from the patient or your parent who's the patient. That would be the same and that would be a four out of eight match. Sometimes by happenstance, the other half that comes from the other parent may also have the region that matches with your partner. So it could be better than four. So at the minimum, it might be a four out of eight, could be a five out of eight match, because the other side also matches a few by just by happenstance. But for these half-match transplants, the minimum you need is four out of eight.

Is there a difference in matches between four out of eight versus eight out of eight or ten out of ten?

So eight out of eight matches are what we prefer. When you do an unrelated donor, if you do a mismatch donor that has higher rates of GvHD when it's an unrelated donor, but when it's a haplo donor where it's only a four out of eight, we do the transplant with a completely different way of transplanting. We call it a transplant with a post-transplantation immunosuppression using a drug called cyclophosphamide. So that way of doing the transplant is radically different from the way we do matched transplants. So the outcomes in terms of GvHD are very similar or even sometimes even better at lower rates of GvHD. So the half-match donors are done in a completely different rate. So, we don't, overall, the way in which the complications are a little bit different in that there is more infection in less GvHD and little less more immunosuppression for haplo transplants.