● `color{violet}("Blood of human")` beings differ in certain aspects though it appears to be similar.

● Various types of grouping of `color{violet}("blood")` has been done.

● Two such groupings – the `color{brown}("ABO and Rh")` – are widely used all over the world.

● `color{violet}("ABO grouping")` is based on the presence or absence of `color{brown}("two surface antigens")` (chemicals that can induce immune response) on the `color{violet}("RBCs")` namely `color{brown}("A and B.")`

● Similarly, the `color{violet}("plasma")` of different individuals contain two natural antibodies (proteins produced in response to antigens).

● During `color{violet}("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 `color{violet}("blood transfusion")` to avoid severe problems of clumping (destruction of RBC).



● From the above mentioned table it is evident that group `color{violet}("‘O’ blood")` can be donated to persons with any other blood group and hence `color{violet}("‘O’ group")` individuals are called `color{brown}("‘universal donors’.")`

● Persons with `color{violet}("‘AB’ group")` can accept blood from persons with `color{violet}("AB")` as well as the other groups of `color{violet}("blood.")`

● Therefore, such persons are called `color{brown}("‘universal recipients’")`

● Another antigen, the `color{brown}("Rh antigen")` similar to one present in `color{brown}("Rhesus monkeys")` (hence Rh), is also observed on the surface of RBCs of majority (nearly 80 %) of humans.

● Such individuals are called `color{brown}("Rh positive")` (Rh+ve) and those in whom this antigen is absent are called `color{violet}("Rh negative (Rh-ve).")`

● An `color{violet}("Rh-ve")` person, if exposed to `color{violet}("Rh+ve blood")`, will form specific antibodies against the Rh antigens.

● Therefore, `color{violet}("Rh group")` should also be matched before transfusions.

● A special case of `color{brown}("Rh incompatibility")` (mismatching) has been observed between the `color{violet}("Rh-ve blood")` of a pregnant mother with `color{violet}("Rh+ve blood")` of the `color{violet}("foetus.")`

● `color{violet}("Rh antigens")` of the foetus do not get exposed to the `color{violet}("Rh-ve blood ")`of the mother in the first pregnancy as the two bloods are well separated by the `color{violet}("placenta.")`

● However, during the delivery of the first child, there is a possibility of exposure of the `color{violet}("maternal blood")` to small amounts of the `color{violet}("Rh+ve blood")` from the foetus.

● In such cases, the mother starts preparing antibodies against `color{violet}("Rh in her blood")`.

● In case of her subsequent pregnancies, the `color{brown}("Rh antibodies")` from the mother `color{violet}("(Rh-ve)")` can leak into the blood of the `color{violet}("foetus (Rh+ve)")` and `color{violet}("destroy the foetal RBCs")`.

● This could be fatal to the `color{violet}("foetus")` or could cause severe `color{violet}("anaemia")` and jaundice to the baby.

● This condition is called `color{brown}("𝘦𝘳𝘺𝘵𝘩𝘳𝘰𝘣𝘭𝘢𝘴𝘵𝘰𝘴𝘪𝘴 𝘧𝘰𝘦𝘵𝘢𝘭𝘪𝘴.")`

● This can be avoided by administering `color{brown}("anti-Rh antibodies")` to the mother immediately after the delivery of the first child.