Which blood type is characterized by the absence of A and B antigens?

Type O blood is characterized by the absence of both A and B antigens on the surface of red blood cells. This means that individuals with Type O blood do not have the specific proteins present that would classify their blood as type A or type B. Consequently, Type O is often referred to as the universal donor type, as it can be given to individuals of any blood type without causing an immune reaction due to the missing antigens.

In contrast, Type A blood has A antigens, Type B has B antigens, and Type AB has both A and B antigens. This distinction is important in blood transfusions, as the presence or absence of these antigens can trigger an immune response if mismatched blood types are mixed. Therefore, Type O blood's unique characteristic of lacking A and B antigens is what defines it and makes it crucial in transfusion medicine.