Biology · Body Fluids and Circulation · NEET
O-group RBCs have no A or B antigens on their surface, so no recipient antibody can attack them, making O the universal donor. AB-group plasma has neither anti-A nor anti-B antibodies, so it cannot clump any donor RBCs, making AB the universal recipient. For NEET, remember: donor status depends on the RBC antigen, recipient status depends on the plasma antibody.
We mainly look at the recipient's plasma antibodies against the donor's RBC antigens. The donor's plasma antibodies get heavily diluted in the recipient's blood, so they matter far less. This is exactly why O (no antigens on RBC) can donate to all even though O plasma has both anti-A and anti-B.
The recipient's antibody binds the matching antigen on donor RBCs and clumps them together. This clumping is called agglutination. The clumped cells block small vessels and later break open (haemolysis), which can be fatal. That is why cross-matching is done before every transfusion.
Both ABO and the Rh factor must be matched. NCERT clearly states the Rh group should also be matched before transfusion. An Rh-negative recipient who gets Rh-positive blood makes anti-Rh antibodies, causing a reaction on the next Rh-positive transfusion.
O-negative RBCs carry no A, no B and no Rh antigen, so its packed cells can go to any ABO/Rh recipient in emergencies. But for safe practice, exact group matching plus cross-matching is still preferred, because minor blood-group systems can also cause reactions.
Persons with "AB" blood group are called "Universal recipients". This is due to:
Select the incorrect statement with reference to Rh grouping. A. Erythroblastosis foetalis is a condition observed having foetus with Rh-ve blood and mother with Rh+ve blood. B. Rh antigen is observed on RBCs in the majority of human beings. C. Before blood transfusion, Rh group should also be matched. D. Rh incompatibility is observed when a pregnant mother is Rh-ve and the foetus is Rh+ve. E. Erythroblastosis foetalis can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of the second child.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The recipient's plasma antibodies must not react with the donor's RBC antigens. If they match, agglutination occurs, so such a pair is incompatible.
O group is the universal donor because its RBCs lack both A and B antigens, so no recipient antibody attacks them. O-negative is preferred as it also lacks the Rh antigen.
AB group is the universal recipient because its plasma has neither anti-A nor anti-B antibodies, so it cannot clump donor RBCs of any group.
An Rh-negative person given Rh-positive blood develops anti-Rh antibodies. On the next Rh-positive transfusion these antibodies cause a severe reaction, so Rh must be matched with ABO.
Agglutination is the clumping of donor RBCs when the recipient's antibody binds the matching antigen. This clumping blocks vessels and destroys cells, making the transfusion dangerous.
