Determination of Weak Rh D antigen
General information:
The term weak D antigen (Du) is used for individuals in whom the Rh(D) antigen is very weakly expressed. Their erythrocytes do not agglutinate or agglutinate very weakly by the anti-Rh(D) sera. Individuals carrying this phenotype can form alloimmune (against foreign antigens) anti-D antibodies during pregnancy and blood transfusion against the missing epitopes in their structure (the fetus can be RhD positive and in this case antibodies can be formed). There are two reasons for having a weak D phenotype:
- Quantitative differences due to missing epitopes in the antigenic structure of the D-antigen. With a series of monoclonal antibodies, it is possible to identify the missing epitopes;
- gene interactions – in this case there are no genetic defects in the antigenic structure, but the expression of the D-antigen is suppressed; (congenital condition)
- The Du phenotype occurs in 0.2-1% of Europeans.
Determination of weak D antigen is carried out at:
- All pregnant women who have a weak Du antigen are defined as Rh(D) negative. They are prevented during pregnancy and after birth with anti-D immunoglobulin. In the period of pregnancy and after birth, they are monitored for the presence of anti-erythrocyte antibodies.
- Blood donors who are Du positive are registered as Rh positive. Their blood is transfused only to Rh positive individuals.
- Du positive patients who require blood transfusion are registered as Rh(D) negative and receive isogroup Rh negative blood to avoid the formation of antibodies against the missing epitopes in their antigenic structure.
The weak D-antigen is immunogenic and can induce antibody formation in Rh negative individuals in cases of blood transfusion and pregnancy. If poorly responsive Du erythrocytes are transfused into a D(-) recipient who has already developed anti-D antibodies, there is little chance that this will result in a clinically significant post-transfusion reaction. If it concerns a pregnant or parturient woman who is Du(+) and the fetus is Rh(D) positive, the pregnant woman may form anti-D antibodies against the missing epitopes.
Sample required:
Venous blood
Key words:
Weak Rh D antigen