Why people with blood type O are known as universal donors?

Individuals with blood type O, often referred to as universal donors, possess the unique advantage of being able to safely donate red blood cells to recipients of almost all other blood types. This broad compatibility stems from the specific characteristics of their blood type.

People with blood type O carry neither the A nor the B antigens on the surface of their red blood cells. These antigens are the substances that trigger an immune response in recipients with incompatible blood types. For instance, individuals with blood type A have anti-B antibodies, which would attack red blood cells carrying the B antigen.

Since blood type O red blood cells lack both A and B antigens, they are less likely to be recognized as foreign by the recipient's immune system. This compatibility allows individuals with blood type O to donate to recipients with blood types A, B, and AB without causing adverse reactions.

Recipients with blood type O can only receive blood from other O individuals to ensure compatibility. This is because their plasma contains both anti-A and anti-B antibodies, which would attack red blood cells carrying either A or B antigens.

While individuals with blood type O are universal donors for red blood cells, it's important to note that blood transfusions also consider compatibility in other blood group systems, such as the Rh factor (positive or negative) and other less common antigens. Therefore, thorough blood typing and crossmatching procedures are still essential to ensure safe transfusions.

In summary, individuals with blood type O are known as universal donors because their red blood cells are compatible with the majority of blood types and pose a lower risk of triggering immune reactions in recipients.