Which type of blood has no agglutinogen?

Type O blood is characterized by the absence of the A and B antigens, also known as agglutinogens, on the surface of its red blood cells. This lack of agglutinogens is significant because it means that type O blood can be considered a universal donor; it can be safely transfused to individuals of any other blood type without the risk of an immune reaction based on these particular antigens.

In contrast, Type A blood has A antigens, Type B blood has B antigens, and Type AB blood has both A and B antigens. Each of these blood types can provoke an immune response in a person with a different blood type due to the presence of these specific agglutinogens, which is not a concern with type O blood. Understanding this crucial difference helps clarify why type O is unique among the blood types, particularly in transfusion scenarios.