The difference in blood groups lies mainly in the difference in blood group antigens on the surface of red blood cells. The blood grouping system commonly used in clinical practice is the ABO blood grouping system, so the ABO blood grouping system is used as an example to illustrate the difference between blood groups.
The ABO blood group system is categorized into four blood types: A, B, O, and AB.
People with blood type A express A antigens on the surface of their red cell membranes, people with blood type B express B antigens on the surface of their red cell membranes, people with blood type AB express both A and B antigens on the surface of their red cell membranes, and people with blood type O do not have associated antigens on the surface of their red cell membranes. With the corresponding antigens on the surface of the red cell membrane, there are no corresponding antibodies in the serum.
People with different blood types cannot transfuse each other’s blood. Although O-type blood is the universal blood, a small amount of O-type blood can be transfused only in special emergency situations.