Which blood type has both the A and B antigens on the surface of the red blood cells and has no antibodies circulating in the plasma?

• A. O
• B. AB
• C. A
• D. B

Answer: (B)

In the ABO system, red blood cells have A and/or B antigens on their surface, and the plasma contains antibodies against the antigens you don’t have. The scenario describes a blood type with both A and B antigens on the red blood cells and no antibodies against A or B in the plasma. That profile belongs to the AB blood type. People with AB blood have both A and B antigens and no anti-A or anti-B antibodies, which is why they are described as universal recipients for ABO-compatible transfusions.

For comparison: type O has neither A nor B antigens and has both anti-A and anti-B antibodies in the plasma; type A has A antigens and anti-B antibodies; type B has B antigens and anti-A antibodies.