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Blood Group: Definition, ABO and Rh Blood Group System

In this article, we will discuss the blood group system: ABO and Rh Blood group System

Blood group system were discovered by Carl Land Steiner.
Human beings have more than 30 types of antigens on the surface of blood cells.
Chemicals that can induce immune response is called antigens.
Antibodies are proteins that protect you when an unwanted substance enters your body.
Various types of grouping of blood has been done.
Two such groupings of blood
1. ABO grouping
2. Rh grouping

1. ABO Blood Group Sytem

ABO grouping is based on the presence or absence of two surface antigens on the RBCs namely A and B.
Similarly, the plasma of different individuals contain two natural antibodies
During mis-matching of blood, the recipients immune system recognises the antigen on donors
RBC and causes clumping (agglutination) of RBCs
O group persons are called universal donors as they can donate blood to persons with any blood group.
AB group persons are called universal recipients because they can accept blood from all groups.

Landsteiner and Weiner (1940) discovered another protein on the surface of red blood corpuscles of rhesus monkey and many human beings. They called it as Rh factor or Rh-antigen.
Nearly 80 percent of humans possess this factor and are Rh positive (Rh+)
Others who do not have this factor are known as Rh negative (Rh–)
Rh positive and Rh negative individuals are normal. The problem arises when an Rh-ve person is exposed to Rh+ve blood during blood transfusion or pregnancy.

A special case of Rh incompatibility has been observed between the Rh–ve blood of a pregnant mother and Rh+ blood of the foetus.
Rh antigens do not get mixed with maternal blood in first pregnancy because placenta separates the two bloods.
But at the time of first delivery, there is a possibility of exposure of the maternal blood to small amounts of the Rh+ve blood from the foetus.
This induces the formation of Rh antibodies in maternal blood.
In case of her subsequent pregnancies, Rh antibodies from mother leak into the foetal blood (Rh+ve) and destroy the foetal RBCs.
This is fatal to foetus or cause severe anaemia and jaundice to the baby. This condition is called Erythroblastosis foetalis.
Erythroblastosis foetalis can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of first child.
Rh antibodies are given to mother with 72 hrs to destroy foetal RBC which prevent Rh-antibodies formation in mother.

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