Human blood group classification

Human blood groups are classified based on specific proteins called antigens on the surface of red blood cells. The most well-known system is the ABO group, which has four types: A, B, AB, and O, depending on the presence or absence of A and B antigens. Another important system is the Rh factor, which indicates whether the Rh antigen is present (+) or absent (−). These classifications are essential for blood transfusions, organ transplants, and pregnancy, as compatibility prevents adverse reactions. Blood grouping ensures safety and compatibility in medical procedures involving blood.