Blood Group Neet

Blood of human beings differ in certain aspects though it appears to be similar. Various types of grouping of blood has been done.
Two such groupings – the ABO and Rh – are widely used all over the world.

ABO grouping

ABO grouping is based on the presence or absence of two surface antigens (chemicals that can induce immune response) on the RBCs namely A and B.
Similarly, the plasma of different individuals contain two natural antibodies (proteins produced in response to antigens).
The distribution of antigens and antibodies in the four groups of blood, A, B, AB and O.
The during blood transfusion, any blood cannot be used; the blood of a donor has to be carefully matched with the blood of a recipient before any blood transfusion to avoid severe problems of clumping (destruction of RBC).
Group ‘O’ blood can be donated to persons with any other blood group and hence ‘O’ group individuals are called ‘universal donors’.
Persons with ‘AB’ group can accept blood from persons with AB as well as the other groups of blood.
Therefore, such persons are called ‘universal recipients’.

Another antigen, the Rh antigen similar to one present in Rhesus monkeys (hence Rh), is also observed on the surface of RBCs of majority (nearly 80
per cent) of humans.
Such individuals are called Rh positive (Rh+ve) and those in whom this antigen is absent are called Rh negative (Rh-ve).
An Rh-ve person, if exposed to Rh+ve blood, will form specific antibodies against the Rh antigens.
Therefore, Rh group should also be matched before transfusions.
A special case of Rh incompatibility (mismatching) has been observed between the Rh-ve blood of a pregnant mother with Rh+ve blood of the foetus.
Rh antigens of the foetus do not get exposed to the Rh-ve blood of the mother in the first pregnancy as the two bloods are well separated by the placenta.
However, during the delivery of the first child, there is a possibility of exposure of the maternal blood to small amounts of the Rh+ve blood from the foetus.
In such cases, the mother starts preparing antibodies against Rh antigen in her blood.
In case of her subsequent pregnancies, the Rh antibodies from the mother (Rh-ve) can leak into the blood of the foetus (Rh+ve) and destroy the foetal RBCs.
This could be fatal to the foetus or could cause severe anaemia and jaundice to the baby. This condition is called erythroblastosis foetalis.
This can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of the first child.

Neet Notes