What determines compatibility in transfusion due to RBC antigens and antibodies?

• A. ABO antigens on RBCs and antibodies in plasma determine compatibility; Rh status matters.
• B. Blood compatibility is determined by white blood cell antigens.
• C. ABO antigens in plasma determine compatibility.
• D. Rh status has no impact on transfusion reactions.

Answer: (A)

The key idea is that transfusion compatibility hinges on matching the antibodies in the recipient’s plasma with the antigens on the donor red blood cells. The ABO system is the most important because people naturally have antibodies to the A or B antigens they do not possess; transfusing blood with incompatible ABO antigens triggers rapid, dangerous hemolysis. The Rh status adds another layer: if an Rh-negative person receives Rh-positive blood, they can develop anti-D antibodies that cause problems with future transfusions or pregnancies. White blood cell antigens aren’t the main factor in RBC transfusion compatibility, and ABO antigens present in plasma aren’t what determine compatibility—the critical interaction is between recipient antibodies in plasma and donor RBC antigens, with Rh matching helping prevent sensitization.