The rhesus system was identified in 1940 by
Landsteiner and Wiener. The discovery followed the detection of an antibody by
Levine and Stetson in 1939 in the mother of stillborn infant who had been
transfused with her husband blood during pregnancy.
Landsteiner and Wiener. The discovery followed the detection of an antibody by
Levine and Stetson in 1939 in the mother of stillborn infant who had been
transfused with her husband blood during pregnancy.
Genetic Basic of the Rhesus
System
System
Five major antigens have been observed in the
rhesus system D, C, c, E and e. C and c as well as E and e are antithetical but
the antithetical antigen for D has never been demonstrated. The term
antithetical refers to two antigens controlled by a pair of allelic genes for
convenience. The allelic gene to D is expressed as d.
rhesus system D, C, c, E and e. C and c as well as E and e are antithetical but
the antithetical antigen for D has never been demonstrated. The term
antithetical refers to two antigens controlled by a pair of allelic genes for
convenience. The allelic gene to D is expressed as d.
The Rh genes reside on the first chromosome with D
gene acting as an autosomal dominant. These genes, the Rh antigens are
transmitted as discrete units (Wiener) as haphotypes (Fisher and Race). An Rh
hapholyte may be thought of as a single “gene” composed of nucleotides sequence
within the gene that encodes multiple individual epilopes (Turgeon, 2005).
gene acting as an autosomal dominant. These genes, the Rh antigens are
transmitted as discrete units (Wiener) as haphotypes (Fisher and Race). An Rh
hapholyte may be thought of as a single “gene” composed of nucleotides sequence
within the gene that encodes multiple individual epilopes (Turgeon, 2005).
The Fisher-Race theory states that there are three
closely-linked inherited as a unit that rarely exhibit crossing over. Each of
these loci contains a primary set of co-dominant allelic gene D and the
theoretic d, C and c or E and e. The gene complex of an antigen is referred to
as the genotype that produces an antigen complex with multiple specificities
(Levine and Stetson, 2009).
closely-linked inherited as a unit that rarely exhibit crossing over. Each of
these loci contains a primary set of co-dominant allelic gene D and the
theoretic d, C and c or E and e. The gene complex of an antigen is referred to
as the genotype that produces an antigen complex with multiple specificities
(Levine and Stetson, 2009).
Rh Phenotypes
In the clinical laboratory, available routine are
used to resolve antibody problems or conduct family studies. The agglutination
reaction of individual erythrocytes with specific Rh antisera produces a
variety of pattern.
used to resolve antibody problems or conduct family studies. The agglutination
reaction of individual erythrocytes with specific Rh antisera produces a
variety of pattern.
Weak D Rhesus Antigen
In serological testing, D positive blood is easily
identified units which are D negative are often retested to rule out a weaker
reaction (Brecher, 2005).
identified units which are D negative are often retested to rule out a weaker
reaction (Brecher, 2005).
In
some cases, this phenotype occurs because of an altered surface protein that is
more common in people of African descent.
The testing is difficult, since using different anti-D reagents,
especially the older polyclonal implication. This is that people with this
sub-phenotype will have a product labelled as “D positive” when
donating blood.
some cases, this phenotype occurs because of an altered surface protein that is
more common in people of African descent.
The testing is difficult, since using different anti-D reagents,
especially the older polyclonal implication. This is that people with this
sub-phenotype will have a product labelled as “D positive” when
donating blood.
When
receiving blood, they are sometimes typed as a “D negative”, though
this is the subject of some most debates. “Weak D” patients can
receive “D positive” blood without complications. However, it is
important to correctly identify the ones that have to be considered D positive
or D negative. This is important, since most blood banks have a limited supply
of “D negative” blood and the correct transfusion is clinically
relevant. In this respect, genotyping of blood groups has much simplified this
detection of the various variants in the Rh blood group system (Avent and Reid,
2009).
receiving blood, they are sometimes typed as a “D negative”, though
this is the subject of some most debates. “Weak D” patients can
receive “D positive” blood without complications. However, it is
important to correctly identify the ones that have to be considered D positive
or D negative. This is important, since most blood banks have a limited supply
of “D negative” blood and the correct transfusion is clinically
relevant. In this respect, genotyping of blood groups has much simplified this
detection of the various variants in the Rh blood group system (Avent and Reid,
2009).
Rhesus Antibodies
In
the rhesus blood group system, naturally occurring rhesus antibodies are not
found in the serum if a person is transfused with Rh positive blood or when Rh
negative woman becomes pregnant with Rh positive foetus and the red cell of the
baby pass with her circulation particularly at the time of delivery stimulating
the production of the anti-D antibody, such circulating anti-D will not become
harmful immediately unless the person receives a transfusion of Rh positive
blood. In such a situation, the donor’s D antigen red cells will be haemolysed
by the anti-D (Cheesbrough, 2006).
the rhesus blood group system, naturally occurring rhesus antibodies are not
found in the serum if a person is transfused with Rh positive blood or when Rh
negative woman becomes pregnant with Rh positive foetus and the red cell of the
baby pass with her circulation particularly at the time of delivery stimulating
the production of the anti-D antibody, such circulating anti-D will not become
harmful immediately unless the person receives a transfusion of Rh positive
blood. In such a situation, the donor’s D antigen red cells will be haemolysed
by the anti-D (Cheesbrough, 2006).
Circulating
immune anti-D antibodies can also cause haemolytic disease of the newborn (HDN)
when a mother with anti-D becomes pregnant with rhesus positive foetus IgG,
anti-D can pass across the placenta into the circulation of the foetus and
destroy foetal red cell in Rh HND. An infant may be stillborn or born jaundiced
with severe haemolytic anaemia. (Scort, 2006).
immune anti-D antibodies can also cause haemolytic disease of the newborn (HDN)
when a mother with anti-D becomes pregnant with rhesus positive foetus IgG,
anti-D can pass across the placenta into the circulation of the foetus and
destroy foetal red cell in Rh HND. An infant may be stillborn or born jaundiced
with severe haemolytic anaemia. (Scort, 2006).
