Which of the following is true in blood transfusion?

Analyze the question: We need the one statement that correctly describes blood transfusion compatibility in the ABO system.

Concept: Compatibility depends on antigens on the red blood cells (donor) and antibodies in the plasma (recipient).

| Group | Antigens on RBCs | Antibodies in plasma | |---|---|---| | A | A | anti-B | | B | B | anti-A | | AB | A and B | none | | O | none | anti-A and anti-B |

• Donor red cells must not carry an antigen that the recipient has antibodies against.
• AB is the universal recipient (no antibodies) and can receive from all groups.
• O is the universal donor (no antigens) and can donate to all groups.

Check each option:

• A. AB can donate only to AB. AB cells carry both A and B antigens. Groups A, B and O all have antibodies against at least one of these, so AB blood can only go safely to AB. This is true, in the sense of red cell transfusion.
• B. A and B donate to or receive from each other. This is false. A has anti-B and B has anti-A, so they would agglutinate each other's blood.
• C. AB can receive only from A or B. This is false. AB can receive from A, B, AB and O, and the word "only" makes it wrong.
• D. O can donate only to O. This is false. O is the universal donor and can give to A, B, AB and O.

Tip: Remember "AB is the universal recipient but a restricted donor; O is the universal donor but a restricted recipient." Any option using the word "only" is usually a trap, so test it against the antigen-antibody table. Here the "only" in A happens to be correct.