Final answer:
O-negative patients are considered universal donors because their blood lacks A, B, and Rh (D) antigens, making it safe to transfuse to any patient, regardless of their blood type.
Step-by-step explanation:
O-negative patients are considered universal donors because their red blood cells lack A, B, and Rh(D) antigens, making their blood compatible with all other blood types in transfusions. The key to understanding this is the antigens present on the surface of erythrocytes. Blood type O has neither type A nor B glycoproteins on their surface, meaning that it does not provoke an immune response when transfused into persons with different blood types, thus it does not cause agglutination. However, O-negative blood is particularly versatile because it also lacks the Rh factor antigen (Rh-), and therefore can be safely given to individuals who are Rh-positive or Rh-negative.
Additionally, the concept of a universal recipient is associated with individuals with AB+ blood type, as they can receive red blood cells from any ABO type. Understanding the mechanisms of blood compatibility is crucial for safe blood transfusions, and type O negative blood can be a lifesaver in emergency situations where there's no time for blood type matching.