Blood type classification

Blood type classification identifies specific markers, called antigens, on the surface of red blood cells. The main systems are ABO and Rh; in ABO, blood is categorized as A, B, AB, or O depending on the presence or absence of A and B antigens. The Rh system indicates whether the Rh factor antigen is present (+) or absent (−). These classifications are crucial for blood transfusions, organ transplants, and pregnancy, as matching blood types reduces the risk of immune reactions that can cause serious health issues.