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There are four main blood groups defined by the ABO system: 1  blood group A has A antigens on the red blood cells with anti-B antibodies in the plasma. 2  blood group B has B antigens with anti-A antibodies in the plasma. 3  blood group O has no antigens, but both anti-A and anti-B antibodies in the plasma.ntroduction. There are four main blood groups (types of blood): A, B, AB and O. Your blood group is determined by the genes you inherit from your parents.
The second most important classification of human blood group is based on Rh antigens. While the ABO classification is based on the two antigens A and B, the Rh group has 50 antigens! However, the main Rh classification is based on one single antigen of special importance, called the D antigen.