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.

2. Rh Blood Group System

• 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.

Rh Incompatibility: Erythroblastosis foetalis

• 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.