Rachel McGhee 1800241
1. The Blood Transfusion Service laboratory assists with the
detection and treatment of Haemolytic Disease of the Foetus and
New-born (HDN).
a. Discuss the formation of a named antibody responsible for
causing HDFN and the mechanism of action of this antibody.
Rh/Anti-D (RhD) positive foetal cells are one of the antibodies responsible
for causing Haemolytic Disease of the Newborn (HDN). The Rh system is
composed of 3 pairs of allelic genes - Cc Dd Ee. D is the most
immunogenic and is the only Rh antigen determined routinely.Anti-D is the
most common cause of HDN. The Rh system is complex and consists of
over 49 related antigens. The genes that control the system are autosomal
codominant. Despite there being only two Rh gene loci RHD and RHCE, the
Fisher-Race theory of three loci, D/d, C/c and E/e is still used for
interpreting serological data. Antigens of the Rh System are proteins in
nature which are developed at birth and the number of antigen sites
depends on the phenotype. HDN can occur if the mother of a child is Anti-
D negative and the Father is Anti-D positive. If an RhD negative mother
has been sensitised to Rh positive blood then her immune system will
create antibodies in response and attack the foetal cells as the RhD
positive foetal cells cause an immune response in the Mother. This
immune response produces (Immunoglobulin G) IgG Anti-D which transfers
across the placenta. IgG then crosses due to the presence of Fc receptors
of placental cells to which the IgG antibodies attach (IgM antibodies
cannot cross only IgG). When the foetal cells cross the placenta they
sensitise the Mother. The Mothers IgG antibodies attack the foetal RhD
positive cells causing problems such as anaemia, haemolysis and a
release of bilirubin. The mothers first pregnancy usually remains
unaffected.
b. Discuss the testing regimes used in the BTS laboratory to screen
for antibodies and what actions would be taken when a clinically
significant antibody is found, both while pregnant and after
delivery.
Antibody screening is carried out to detect clinically significant antibodies
that may affect foetus or newborn and to highlight future transfusion
problems. Antibody specificity may indicate clinical significance. To
identify the antibody measurement of the strength of antibodies and
identification of additional antibodies may be carried out. Follow up tests
where alloantibodies detected may be required to monitor strength of
antibodies, identify pregnancies at risk of Haemolytic Disease of the
Foetus and Newborn and to predict neonates that require treatment. RhD
negative women are screened from Rh throughout their pregnancy.When
a bleed at delivery occurs an anti-D injection is given to the mother which
neutralises fetal red cells that have crossed the placenta and protects
mothers immune system by preventing a response preventing formation
of allo anti-D. Additionally, 1500 iu Anti-D is given routinely at 28 weeks. If
an Rh Pos baby is delivered, the Mother is given 500iu Anti-D.
Anti-D can be given in the following circumstances: Amniocentesis,
Abdominal Trauma, Antepartum Haemorrhage, Ectopic pregnancy,
1. The Blood Transfusion Service laboratory assists with the
detection and treatment of Haemolytic Disease of the Foetus and
New-born (HDN).
a. Discuss the formation of a named antibody responsible for
causing HDFN and the mechanism of action of this antibody.
Rh/Anti-D (RhD) positive foetal cells are one of the antibodies responsible
for causing Haemolytic Disease of the Newborn (HDN). The Rh system is
composed of 3 pairs of allelic genes - Cc Dd Ee. D is the most
immunogenic and is the only Rh antigen determined routinely.Anti-D is the
most common cause of HDN. The Rh system is complex and consists of
over 49 related antigens. The genes that control the system are autosomal
codominant. Despite there being only two Rh gene loci RHD and RHCE, the
Fisher-Race theory of three loci, D/d, C/c and E/e is still used for
interpreting serological data. Antigens of the Rh System are proteins in
nature which are developed at birth and the number of antigen sites
depends on the phenotype. HDN can occur if the mother of a child is Anti-
D negative and the Father is Anti-D positive. If an RhD negative mother
has been sensitised to Rh positive blood then her immune system will
create antibodies in response and attack the foetal cells as the RhD
positive foetal cells cause an immune response in the Mother. This
immune response produces (Immunoglobulin G) IgG Anti-D which transfers
across the placenta. IgG then crosses due to the presence of Fc receptors
of placental cells to which the IgG antibodies attach (IgM antibodies
cannot cross only IgG). When the foetal cells cross the placenta they
sensitise the Mother. The Mothers IgG antibodies attack the foetal RhD
positive cells causing problems such as anaemia, haemolysis and a
release of bilirubin. The mothers first pregnancy usually remains
unaffected.
b. Discuss the testing regimes used in the BTS laboratory to screen
for antibodies and what actions would be taken when a clinically
significant antibody is found, both while pregnant and after
delivery.
Antibody screening is carried out to detect clinically significant antibodies
that may affect foetus or newborn and to highlight future transfusion
problems. Antibody specificity may indicate clinical significance. To
identify the antibody measurement of the strength of antibodies and
identification of additional antibodies may be carried out. Follow up tests
where alloantibodies detected may be required to monitor strength of
antibodies, identify pregnancies at risk of Haemolytic Disease of the
Foetus and Newborn and to predict neonates that require treatment. RhD
negative women are screened from Rh throughout their pregnancy.When
a bleed at delivery occurs an anti-D injection is given to the mother which
neutralises fetal red cells that have crossed the placenta and protects
mothers immune system by preventing a response preventing formation
of allo anti-D. Additionally, 1500 iu Anti-D is given routinely at 28 weeks. If
an Rh Pos baby is delivered, the Mother is given 500iu Anti-D.
Anti-D can be given in the following circumstances: Amniocentesis,
Abdominal Trauma, Antepartum Haemorrhage, Ectopic pregnancy,
