Final answer:
The special antigens on red blood cells, called agglutinogens, are glycoproteins that are critical for determining blood type and are important to avoid agglutination during blood transfusions.
Step-by-step explanation:
The special antigens on red blood cells are called agglutinogens. These are specifically glycoproteins or glycolipids that are present on the surface of red blood cells and determine an individual's blood type. The ABO and Rh blood group systems are the most well-known, with the ABO system comprised of antigen A and antigen B. Individuals with blood type A possess antigen A, those with blood type B have antigen B, those with AB have both, and those with blood type O have neither antigen. These surface antigens are recognized by the body's immune system and play a critical role in blood transfusions and immune reactions. For example, when type A and type B blood are combined, agglutination (clumping) occurs because of the opposing antibodies in the plasma, which can lead to serious health complications.