Erythrocyte transfusion

In medicine, erythrocyte transfusion or red blood cell transfusion is the "transfer of erythrocytes from a donor to a recipient or reinfusion to the donor."

Blood group incompatibility
A blood group incompatibility is a "mismatch between donor and recipient blood. Antibodies present in the recipient's serum are directed against antigens in the donor product. Such a mismatch may result in a transfusion reaction in which, for example, donor blood is hemolyzed."