Blood type compatibility, determined by protein signatures on red blood cells, is the first step in matching donors and recipients for transplantation.

“kind of the protein signature on the coating of those red blood cells and they we know that if you give someone who uh carries blood of a certain type a blood type that is incompatible so let's make it the simplest someone who has blood type a and someone who has blood type b and you give the individual with blood type a blood from an individual with blood type b the they will uh have antibodies that attack those blood cells and essentially destroy the blood cells because they think they are recognized as foreign”