Question

• Explain the role of ABO antigens in transfusion reactions and the role of the Rh antigen in hemolytic disease of the newborn.

Answer 1

ABO grouping is a test performed to determine an individual's blood type.

It is based on the premise that individuals have antigens on their red blood cells (RBCs) that correspond to the four main blood groups: A, B, O, and AB. Antibodies (isohemagglutinins) in an individual's plasma are directed against blood group antigens that their own RBCs lack. These antibodies (isohemagglutinins) form early in life.

ABO antigens are expressed on RBCs, platelets, and endothelial cells and are present in body fluids.

ABO testing is performed to prevent an adverse transfusion reaction that could be caused by ABO incompatibility between the blood of a patient (recipient) and that of a donor.

ABO incompatible transfusion reaction is an acute haemolytic transfusion reaction. This reaction can lead to haemostatic and complement activation and result in shock and renal failure. So ABO compatibility checking is essential for blood transfusions.

The presence of RhD antigen on red cells confers Rh positivity and people who lack RhD antigen are Rh negative.

Exposure of Rh negative individuals to even small amounts of Rh positive cells, by either transfusion or pregnancy, can result in the production of Rh antibodies which are mainly IgG type.

All Rh alloantibodies should be considered potentially capable of causing Haemolytic disease of the fetus and newborn (severe cases with anti-D and anti-c and mild to moderate cases with anti-C, anti-E and anti-e).

Hemolytic diseases of the newborn occurs when the baby's red blood cells break down at a fast rate. It happens when an Rh negativemother has a baby with an Rh positive father. If the Rh negative mother has been sensitized to Rh positive blood, her immune system will make antibodies to attack her baby.