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Rh Blood Group
The Rhesus or Rh antigen is a class of agglutinogen on the red blood cells or RBCs. Its presence or absence categorizes a person as Rh-positive or Rh-negative.
When reporting a person's blood group, the Rh antigen is typically combined with the A and B antigens.
For instance, the blood type of a person with antigens A and Rh is designated as A-positive. Conversely, in the absence of Rh antigen, the person's blood is referred to as A-negative.
Unlike the ABO system, the plasma does not naturally contain anti-Rh antibodies.
So, exposure to the Rh antigen can trigger an immune response in Rh-negative individuals, leading to hemolysis.
For example, suppose an Rh-negative mother carries an Rh-positive fetus. In that case, the mother's immune system recognizes the Rh antigen on the fetal RBCs as foreign, triggering the production of anti-Rh antibodies.
Typically, these antibodies do not interfere in the first pregnancy. However, in subsequent pregnancies with Rh-positive fetuses, the fetal RBCs are at risk of hemolysis due to the existing anti-Rh antibodies in the mother's blood.
22.26:
Rh Blood Group
The Rhesus (Rh) antigen is crucial in determining blood groups and ensuring compatibility during blood transfusions.
The Rhesus Antigen and Blood Groups
The Rh antigen is a protein found on the surface of red blood cells (RBCs) in most individuals. Its presence or absence classifies a person's blood type as Rh-positive or Rh-negative. For instance, if someone with blood type A has the Rh antigen, they are classified as A positive (A+). Without the Rh antigen, their blood group is A negative (A-). Understanding the Rh factor is essential in transfusion medicine because incompatible Rh factors between donor and recipient can trigger an immune response, leading to blood cell destruction, or hemolysis, and potential complications.
The Role of the Rh Antigen in Hemolytic Disease of the Newborn
The importance of the Rh antigen is particularly evident in pregnancy, specifically in hemolytic disease of the newborn (HDN). HDN occurs when there is an incompatibility between the Rh factors of the mother and fetus. Suppose an Rh-negative mother carries an Rh-positive fetus. In that case, her immune system may recognize the Rh antigen on the fetal RBCs as foreign, triggering the production of anti-Rh antibodies. In a first pregnancy, this typically does not cause problems. However, if the mother becomes pregnant again with an Rh-positive fetus, the anti-Rh antibodies from the first pregnancy can cross the placenta and attack the second fetus's Rh-positive RBCs, leading to hemolysis and HDN.
Preventing Hemolytic Disease of the Newborn
Given the risks associated with Rh incompatibility, preventive measures are essential. Rh-negative mothers often receive an injection of RhoGAM, a serum containing anti-Rh antibodies, during and after the birth of an Rh-positive baby. This prevents the mother's immune system from recognizing the Rh antigen as foreign, thereby stopping the production of anti-Rh antibodies and reducing the risk of HDN in subsequent pregnancies.
In conclusion, the Rh antigen plays a vital role in transfusion medicine, particularly in blood grouping and compatibility. Understanding its significance, especially concerning HDN, enables the implementation of effective preventive strategies to safeguard maternal and newborn health.