What determines someone’s blood type?
There are many different types of blood a person could have. There are 4 main types of blood A, AB, B, and O. Determining blood types is all about the presence or absence of two antigens. These antigens are either A or B and their on the surface of red blood cells. An antigen is a foreign substance that will induce an immune system response in the body. A person with blood type A has the A antigen on the surface of the red blood cells. Blood type B has the B antigen and type AB has both A and B antigens on the cells surface. The last main type of blood, type O has neither A nor B on the surface. Along with the 4 main groups of blood someone could be Rh positive or Rh negative. Being positive or negative with the Rh factor is due to a third antigen called the Rh factor. If the antigen is present the blood will be Rh-positive and if it is absent the blood would be Rh-negative. Putting all that information together that means if someone tested positive for antigen B and tested negative for the Rh factor that means that person would have type B(-) blood.