Hi @asarnesejr Donors for a stem cell transplant are chosen by how closely certain markers, called Human leukocyte antigens (HLA) match up to your current immune system. With the transplant, you’d be receiving that donor’s immune system as your own so a close match is important. Also, as a side note, blood type matching isn’t important. It’s the HLA markers.

Standard testing looks at four pairs of HLA markers, called 8/8 matching. More detailed testing adds a fifth pair (DQB1) to make 10/10 matching.
So a 7/8 match, if there are no other options is considered an acceptable HLA match.
Here’s how donors are chosen.
Cancer.org https://www.cancer.org/cancer/managing-cancer/treatment-types/stem-cell-transplant/finding-a-donor.html

There’s a lot to absorb, I know. I have resource links to send you if you’re interested in more info.