Rh Incompatibility

Rh Incompatibility

What is the basis of classification of blood groups and what are the uses of blood grouping? Add a note on Rh+ blood. (or) Rh incompatibility. (or) Rh group.
Answer:

Classification of blood groups:

• It is based on the presence or absence of a specific agglutinogen or antigen on the surface of the red cell membrane.

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• The most important blood groups are:

1. ABO system.

• It is based on the presence of absence of antigen A and antigen B blood is divided into 4 groups.

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2. Rh Blood group.

• Rh factor is an antigen present in RBC.
• It was first discovered by Landsteiner and Weiner in rhesus monkey.
• The persons having D antigen are called Rh positive and those without D antigen are called Rh negative.
• Rh antibodies are of the IgG type and the antigen – antibody reaction occurs best at the body temperature.

Principles of blood grouping:

• Blood grouping is done on the basis of agglutination which means clumping of RBCs
• Agglutination occurs when a specific antigen called iso aggulatinin.
• Thus, agglutination occurs when antigen A is mixed with Anti-A or when antigen B is mixed with Anti-B.

Uses of blood grouping:

• In blood transfusion to avoid blood transfusion reactions.
• For matching tissues during organ transplantation.
• Investing cases of paternity disputes.
• If one knows his/her blood group, it may be helpful in emergency conditions.
• In pregnancy to prevent the complications due to Rh incompatibility.
• For research purposes.
• Anthropological purposes.

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Rh blood:

• Rh blood group system is not detected in tissues other than RBCs.

Rh blood Inheritance:

• Rh factor is an inherited dominant factor.
• It is inherited from both the parent.
• It may be homozygous positive DD, heterozygous negative Dd, or homozygous negative dd.

Rh antibody:

• It is not usually present in the plasma.
• But, its production can be evoked in Rh negative individuals by.
• Transfusion with Rh positive blood.
• Entrance of Rh-positive blood from foetus into the circulation of Rh negative mother.

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Rh  Complication:

1. When Rh negative person receives Rh positive blood for the first time, he is not much effect but antibodies are produced within one month.
   • These are lysed by macrophages and a mild delayed transfusion reaction occurs.
   • But when the received Rh positive blood for the second time, severe transfusion reaction occurs immediately which may lead to jaundice, cardiac shock or renal shutdown.
2. When a Rh negative mother carries a Rh positive fetus, usually the first child escapes the complications of Rh incompatibility.
   • At the time of delivery the Rh antigen from foetal blood leaks into mother’s blood.
   • When the mother conceives for the second time and if the fetus happens to be Rh positive again, the Rh antibody from mother’s blood enters the fetal blood.
   • This causes agglutination of fetal RBCs resulting in hemolysis.

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Rh  Prevention:

• Anti D should be administered to the mother at 28th and 34th weeks of gestation.
• Anti D should be administered to the mother within 48 hours after delivery.