In the early 20th century, Karl Landsteiner, an Austrian scientist, classified blood according to the two distinct differences found within the blood. Karl Landsteiner observed the surface of the red blood cells and found two distinct chemical molecules. He labeled one molecule "A" and the other molecule "B." When a red blood cell only had “A” molecules, it was called type A. When a red blood cell with only “B” molecules, it was called type B. A red blood cell with a mixture of both molecules was called type AB. If a red blood cell had neither molecule, that blood was called type O. It was later learned that mixing two blood types could result in clumps within the blood vessel, producing a fatal result. Therefore, it is extremely important for blood type to be matched before a blood transfusion. Every blood type can donate blood to itself. A person with type O blood can donate to all of the other blood types, while people with type A or B can donate to type AB. A person with type A blood can receive from both a person with type A or type O. A person with type B blood can receive from both a person with type B or type O. A person with type AB blood can receive from anyone. A person with type O blood can receive blood only from a person with type O. People with type O blood are known as universal donators, which people with type AB blood are known as universal receivers. Rh status is another factor in blood donation. Your Rh status can be either positive (+) or negative (-). There is a chance, if you have Rh- blood, that your body may form antibodies against Rh+ blood. This can result in the destruction of the Rh+ blood. When this happens, you must have first been exposed to Rh+ blood. This can happen through a blood transfusion or when you carry an Rh+ fetus. If you have antibodies against Rh+ blood and are pregnant with an Rh+ fetus, it is a problem. This problem can be solved with the new medication for preventing this reaction. This medicine must be given immediately after you are exposed to Rh+ blood. Children won’t always have the same blood type or Rh status as their parents. If your blood type is.... Type You Can Give Blood To You Can Receive Blood From A+ A+  AB+ A+  A-  O+  O- O+ O+  A+  B+  AB+ O+  O- B+ B+  AB+ B+  B-  O+  O- AB+ AB+ Everyone A- A+  A-  AB+  AB- A-  O- O- Everyone O- B- B+  B-  AB+  AB- B-  O- AB- AB+  AB- AB-  A-  B-  O-