Rh Factor


 
 
Concept Explanation
 

Rh Factor

Rh Grouping / Factor

Apart from the antigens discussed in the previous section, another antigen, known as Rh antigen (similar to the one present in Rhesus monkey) is also found on the RBCS surface in majority of humans (nearly about 80%). Individuals having Rh antigen are called Rh positive (Rh^+) and those without the Rh antigen are called Rh negative (Rh^-).

Rh group is mandatory to be matched before transfusion of blood is done. An Rh^-  person if gets exposed to Rh^+  blood, it will form specific antibodies against the Rh antigens. Rh Incompatibility During Pregnancy : -  A special case of mismatching of Rh group or Rh incompatibility has been observed between the Rh^-  blood of a pregnant mother with Rh^+  blood of the foetus (the foetus of Rh woman and a Rh^+ man).

In such a case, mother becomes sensitive, while carrying an Rh^+  baby in her womb. The reason is that some of the RBCS from the developing foetus enter into the bloodstream of the mother during development. This causes the development of anti-Rh antibodies in mother's blood.

The Rh antigens of the foetus do not get exposed to the Rh blood of the mother in case of first pregnancy (because two blood remain separated by placenta).

However, during delivery of the first child, there occurs a possibility that maternal blood may get exposed to small amounts of Rh blood from the foetus. Hence, preparing antibodies against Rh antigens in her blood. Thus, in case of her subsequent pregnancies, Rh foetuses get exposed to the anti-Rh antibodies. These antibodies will reach the blood of the foetus (Rh *) and destroy foetal RBCS.

This could be fatal to the developing foetus and could cause severe anaemia and jaundice to the developing baby. This is known as erythroblastosis foetal is or haemolytic disease of newborn.

Precautions : - 

1. This condition can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of the first child.

2. Rh factor was discovered by Landsteiner and Weiner (1940) after immunising the rabbits with the blood of a monkey (Macaca rhesus).

3. There are 30 or so, known antigens on the surface of red blood çells that give rise to different blood groups, eg., MN, etc.

 
 
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