Packed red blood cells do not have an antibody, since the greatest risk of Rh incompatible blood is to current or future pregnancies. For RBCs, type O negative blood is considered a "universal donor" as recipients with types A, B, or AB can almost always receive O negative blood safely. Type AB positive is considered a "universal recipient" because they can receive the other ABO/Rh types safely. These are not truly universal, as other red cell antigens can further complicate transfusions. There are many other human blood group systems and most of them are only rarely associated with transfusion problems. A screening test is
Blood ritual The Aztecs believed the gods would provide plentiful crops and healthy long lives as long as blood was ritually given (Pendragon 2). If blood was not sacrificed to the gods, the humans believed they would be punished and endure excessive pain “more violent than any man could ever do” (Pendragon 3). Some Indians practice a political ritual voluntarily where the people donate blood as a way to remember politicians who have died (Copeman 126). The blood donation is literally a donation to people who need transfusions (Copeman 132). The participants donate at donation camps during the birthday or the anniversary