What are ABO blood groups?
Blood types are classified in several ways. The most basic system is called ABO, which divides blood into four groups, or types: A, B, AB and O. There are two distinct antigens (a type of protein) present on the surface of some people’s red blood cells. Each person’s blood contains a specific and inherited set of these. In the ABO system, one antigen is labeled “A” and the other “B.” If the red blood cell has only A antigen on it, that blood is called “type A”. If the red blood cell has B antigen only, that blood is called “type B”. If the red blood cell has both A and B antigens, the blood is called “type AB”. If the red blood cell has neither antigen, the blood is called “type O”. In a group of 100 people, on average: • 45 are type O • 40 are type A • 0 are type B • 5 are type AB. This varies among different ethnic populations. A small percentage of people have rare blood types, which appear as an unusual and sometimes extensive series of letters in addition to their ABO type. A bloo
