Biology · Body Fluids and Circulation · NEET
The Rh factor is an ANTIGEN present on the surface of RBCs, just like the A and B antigens of ABO grouping. It is not an antibody. If this antigen is present the person is Rh+ve; if absent, Rh-ve. Students often confuse this because ABO groups talk about both antigens and antibodies, but for Rh, NCERT only names the Rh antigen.
NCERT states that nearly 80 per cent of humans have the Rh antigen on their RBCs and are therefore Rh positive. The remaining ~20% lack it and are Rh negative. This exact figure is a common NEET fact, so remember 'nearly 80%'.
No. Unlike ABO grouping (where antibodies are present naturally in plasma), an Rh-ve person does NOT carry anti-Rh antibodies by birth. The antibodies form only AFTER the person is exposed to Rh+ve blood, for example through a mismatched transfusion or an Rh+ve foetus. This is a key difference NEET likes to test.
If an Rh-ve person receives Rh+ve blood, they start making specific antibodies against the Rh antigen. On a second exposure these antibodies can clump (agglutinate) and destroy the donor's Rh+ve RBCs. So NCERT clearly says the Rh group should also be matched, in addition to the ABO group, before transfusion.
ABO grouping is based on A and B antigens and the plasma always has the matching antibodies from birth. Rh grouping is based on a single Rh antigen, and anti-Rh antibodies are NOT present naturally; they appear only after exposure to Rh+ve blood. Both must be matched for a safe transfusion.
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.
Rh stands for Rhesus, because the Rh antigen was first found in Rhesus monkeys and later seen on human RBCs.
Yes, because Rh+ve people can carry a hidden Rh-negative gene. NEET focuses on the antigen concept, so remember: present = Rh+ve, absent = Rh-ve.
No. Rh grouping matters both for safe blood transfusion and for Rh incompatibility during pregnancy. NCERT covers both uses.
Rh+ve is far more common. NCERT gives nearly 80% of humans as Rh positive.
