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:

• Blood group A: A antigens on red cells, anti-B antibodies in plasma
• Blood group B: B antigens, anti-A antibodies
• Blood group AB: both A and B antigens, no antibodies (universal recipient)
• Blood group O: no antigens, both anti-A and anti-B antibodies (universal donor)

A donor's red cells must not carry an antigen that the recipient's plasma has antibodies against.

Checking each option:

A. AB can donate only to AB. AB red cells carry both A and B antigens. Recipients of groups A, B and O all have antibodies against at least one of these, so their blood would clump the donated cells. Only AB recipients lack both antibodies. So this is true.

B. A and B can donate to or receive from each other. False. Group A blood has anti-B antibodies, so it would react with B cells, and vice versa.

C. AB can receive blood only from A or B. False. AB can receive from A, B, AB and O, and the statement also leaves out AB and O donors.

D. O can donate only to O. False. O is the universal donor and can give to A, B, AB and O.

Tip: Remember "AB gets from all, gives only to AB" and "O gives to all, gets only from O". Think of antigens on the donor's cells and antibodies in the recipient's plasma, and check that they never meet in a matching pair.