Why can individuals with type O blood donate to any ABO type, and from whom can they receive blood?

• A. Type O RBCs lack A and B antigens; Type O individuals have anti-A and anti-B antibodies in plasma
• B. Type O RBCs carry A and B antigens
• C. Type O is universal recipient
• D. Type O can donate only to AB

Answer: (B)

The key idea is that compatibility in ABO transfusions depends on antigens on red blood cells and antibodies in plasma. Type O red blood cells lack both A and B antigens, so they won't be targeted by the recipient’s anti-A or anti-B antibodies, allowing them to be given to any ABO type. However, individuals with type O have anti-A and anti-B antibodies circulating in their plasma, so receiving blood from someone with A, B, or AB antigens would trigger a reaction. Therefore, they can only receive blood from type O donors. In short, lack of A and B antigens on type O cells enables universal donation for red cells, while their own antibodies restrict their sources of transfusion to type O.