How the donor DNA match works

When we talk about finding a “donor match” for Bethany, I’ve been using the term “DNA markers”, which is not technically inaccurate, but it is probably less specific than it could be.

What they’re really looking for are “HLA markers” or “human leukocyte antigen” markers that match. These markers “contain a large number of genes related to immune system function in humans.” And “the immune system uses the HLAs to differentiate self cells and non-self cells. Any cell displaying that person’s HLA type belongs to that person and therefore is not an invader.”

These are the little guys who can both kill off any remaining cancer cells, and cause the maddening array of graft vs host (GVH) difficulties that bone marrow transplant (BMT) patients must deal with.

The diagram here shows you probably as much as I could ever hope to tell you about them. I wish I’d had this diagram when talking with Renee at our first intake meeting. These markers are key among the ones that need to match in order to find a suitable donor.

As I’ve noted, Bethany has a rare “C” marker. I could not honestly tell you what that means, other than that it is a very important one. I am happy, at this point, to know as much as I do about it.

The last time I talked with Renee (on Monday), there was one person (among the four remaining candidates who matched 10/10 of these HLA markers) who had already submitted to the further blood testing that was needed, and a second one was scheduled for this testing.

Again, my understanding is that all of these four individuals had characteristics (older, females with multiple antigen-causing pregnancies, etc.) that made them less than ideal candidates. Though, as 10/10 matches, they are suitable.

There is a second group of four individuals, who match on the critical “C” marker, but may be mismatched in some other way. (These individuals might potentially become 8/10, 9/10, or 10/10 matches, but at least they will match the critical “C” marker). These folks are also being asked to undergo some further testing.

It’s a big process, and honestly, I wish things were a bit further along than they were. But 10 years ago, I don’t believe Bethany would have had the option of a transplant. She would simply have been forced to live out a short remaining life span, full of blood transfusions and a chemotherapy regimen that would eventually fail.