51For a blood donor and recipient to be ABO-compatible for a transfusion, the recipient cannot be able to produce anti-A or anti-B antibodies that correspond to the A or B antigens on the red blood cells (since the red blood cells are isolated fro the whole blood before transfusion, it is unimportant whether the donor's blood has antibodies in its plasma). If the antibodies of the recipient's blood and the antigens on the donor's red blood cells do correspond the donor's blood is rejected. In addition to the ABO-system, the Rh-blood group system can affect transfusion compatibility. An individual is either positive or negative for the Rh-factor; tat is denoted by a'+' or '-' after their ABO type. Blood that is Rh-negative can be transfused to Rh-positive, but an Rh-negative individual can create antibodies for Rh-positive RBCs. Because of this AB+ blood is referred to as 'universal recipient', as it possesses neither anti-A nor anti-B antibodies in its plasma, and can receive both Rh-negative and Rh-positive blood, Similarly, the O-blood type is called 'universal donor' since its red blood cells have no A or B antigens and are Rh-negative, no other blood type will reject it.
