Blood transfusion reaction A hemolytic transfusion reaction is a
serious problem that occurs after a patient receives a
transfusion of blood. The red blood cells that were given to the
patient are destroyed by the patient's immune system. There are
other types of allergic transfusion reactions that do not cause
hemolysis. Blood is classified into different blood types called
A, B, AB, and O. Your immune system can usually tell its own
blood cells from blood cells from another person. If other blood
cells enter your body, your immune system may make antibodies
against them. These antibodies will work to destroy the blood
cells that your immune system does not recognize. Another way
blood cells may be classified is by Rh factors. People who have
Rh factors in their blood are called "Rh positive." People
without these factors are called "Rh negative." Rh negative
people form antibodies against Rh factor if they receive Rh
positive blood. There are also other factors to identify blood
cells, in addition to ABO an