~~April 15, 2014~~
BY POPULAR DEMAND: A handy blood type chart for you.
Although all blood is made of the same basic elements, not all blood is alike. In fact, there are eight different common blood types, which are determined by the presence or absence of certain antigens – substances that can trigger an immune response if they are foreign to the body. Since some antigens can trigger a patient’s immune system to attack the transfused blood, safe blood transfusions depend on careful blood typing and cross-matching.
THIS IS WHY IT’S SO IMPORTANT THAT BLOOD TYPES BE DETERMINED PRIOR TO BLOOD TRANSFUSIONS. TYPES HAVE TO BE COMPATIBLE TO PREVENT A NEGATIVE REACTION WHICH COULD ULTIMATELY END IN DEATH
There are four major blood groups determined by the presence or absence of two antigens – A and B – on the surface of red blood cells:
- Group A – has only the A antigen on red cells (and B antibody in the plasma)
- Group B – has only the B antigen on red cells (and A antibody in the plasma)
- Group AB – has both A and B antigens on red cells (but neither A nor B antibody in the plasma)
- Group O – has neither A nor B antigens on red cells (but both A and B antibody are in the plasma)
In addition to the A and B antigens, there is a third antigen called the Rh factor, which can be either present (+) or absent ( – ). In general, Rh negative blood is given to Rh-negative patients, and Rh positive blood or Rh negative blood may be given to Rh positive patients.
- The universal red cell donor has Type O negative blood type.
- The universal plasma donor has Type AB positive blood type.
In 1901, scientist Karl Landsteiner reported that blood could be classified into “types.” By matching these blood types, a successful blood transfusion could be made between a healthy donor and a patient in need of blood. Today, hospital blood banks maintain an assortment of blood products (red blood cells, plasma, platelets, etc) in a variety of blood types.
There are four main blood types: A, B, AB, and O. Each of these blood types is either RH positive (+) or Rh negative (-). So, if someone has type B blood, they have either B+ or B- blood.
The blood type of a patient determines which blood types they are able to receive as a transfusion. The blood type of a blood donor also determines who can receive their blood donation.
These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system. Some of these antigens are also present on the surface of other types of cells of various tissues. Several of these red blood cell surface antigens can stem from one allele (or very closely linked genes) and collectively form a blood group system.
Blood types are inherited and represent contributions from both parents. A total of 32 human blood group systems are now recognized by the International Society of Blood Transfusion (ISBT). The two most important ones are ABO and the RhD antigen; they determine someone’s blood type (A, B, AB and O, with + and – denoting RhD status).
Many pregnant women carry a fetus with a blood type different from their own, and the mother can form antibodies against fetal RBCs. Sometimes these maternal antibodies are IgG, a small immunoglobulin, which can cross the placenta and cause hemolysis of fetal RBCs, which in turn can lead to hemolytic disease of the newborn called erythroblastosis fetalis, an illness of low fetal blood counts that ranges from mild to severe. Sometimes this is lethal for the fetus; in these cases it is called hydrops fetalis.