ABO BLOOD GROUPING IS DIVIDED IN TO 4 TYPE OF BLOOD GROUP 1 A 2 B 3 AB 4 O TYPE AB IS KNOWN AS A UNIVERSAL RECIPIENT TYPE O KNOWN AS A UNIVERSAL DONOR

1. ABO BLOOD GROUPING
AND RHUSESE FACTOR
LEZAN IBRAHIM HAMADAMIN SORKAN | 2nd
GENERAL MEDICINE | 21/2/2019

2. Introduction to blood types
− All cells, including those that make up blood, have a combination of substances
known as antigens on their surfaces that is inherited. Antigens function to enable
our immune system to distinguish the body’s own cells from foreign invaders. When
invaders are recognised, they are destroyed by antibodies, which are also produced
by the immune system. In blood typing, antigens on the surfaces of red blood cells
(RBCs) are also known as agglutinogens and the antibodies that react against them
are also called agglutinins. Antibodies in the blood are found in the plasma.

3. The ABO blood group
− The ABO blood groups are made up of 4 types of blood –
− A, B, AB and O. An individual’s ABO blood type is
determined by the hereditary presence or absence of the
antigens A and B on the surfaces of RBCs. Antibodies of the
ABO group appear in the plasma 2-8 months after birth
mainly in response to the bacteria that inhabit the
intestines. However, antibodies cross-react with RBC
antigens that are different to those present on the
individual’s own RBCs. This cross-reaction can be fatal and
therefore has great significance in blood transfusions.

6. Identifying ABO blood types
People with type A blood have the antigen A on the surface of their RBCs,
while people with type B blood have the B antigen.
Individuals with type AB blood have both A and B antigens, whereas people
with type O blood have no antigens present (there is no antigen O). The
antibody that reacts against antigen A is called anti-A, and is found in the
plasma of people who do not possess antigen A on their own RBCs – that
is, people with type O or type B blood. The antibody that reacts against
antigen B is called anti-B and is present in those who do not possess
antigen B in their RBCs – people with type O or type A blood.

8. Importance of ABO blood groups in
transfusions
An antibody can attach to several RBCs at once and
bind them together. Agglutination is the clumping of
RBCs bound together by antibodies. In giving
transfusions, it is very important that the donor’s
RBCs not agglutinate as they enter the recipient’s
bloodstream.
For example, if type B blood (with B antigens) were
transfused into a type A recipient (with anti-B
antibodies), the recipient’s anti-B antibodies would
immediately agglutinate the donor’s RBCs

9. , causing a transfusion reaction where the agglutinated RBCs block small
vessels and release their haemoglobin (Hb) over the next few hours to days.
This free Hb can block the kidney tubules and cause death from kidney failure
within a day or so. Therefore, a person with type A (anti-B) blood cannot
receive B or AB blood, a person with type B (anti-A) blood cannot receive A or
AB blood, and a person with type O (anti-A and ant-B) blood cannot receive
A, B or AB blood.
Type AB blood is sometimes called the universal recipient because it lacks
both anti-A and anti-B antibodies, so it will not agglutinate donor RBCs of any
ABO type.
Type O may sometimes be called the universal donor, because since there is
no “anti-O” antibody, recipients of any ABO type may receive type O blood.

10. Type O Type A Type B Type AB
RBC Antigen
present
None A B A, B
Plasma
antibody
present
Anti-A, Anti-B Anti-B Anti-A None
Compatible
donor RBC
O O, A O, B O, A, B, AB
Incompatible
donor RBC
A, B, AB B, AB A, AB None

11. The Rhesus blood group
The Rhesus or Rh blood group is named after
the rhesus monkeys in which they were first
discovered. Individuals either belong to the Rh-
positive (Rh+) or Rh-negative (Rh-) Rhesus
blood group. People with the Rh+ blood group
have D antigens on the surface of their red
blood cells, while Rh- individuals do not.

12. In contrast to the ABO group, anti-D antibodies that react against D antigens
are not usually present in the blood under normal conditions. They only form in
Rh- individuals who are exposed to Rh+ blood. If an Rh- receives an Rh+
transfusion, the recipient produces anti-D antibodies. Since anti-D does not
form instantaneously, there is little danger in the first mismatched transfusion.
However, because the recipient will now start producing anti-D, a subsequent
Rh+ transfusion could agglutinate the donor’s RBCs.

13. Implications of Rhesus blood groups during
pregnancy
A related condition can occur when a Rh- woman is pregnant with a Rh+
foetus. The first pregnancy is generally uneventful since anti-D does not form
right away, so that even if the mother is exposed to Rh+ foetal blood via
miscarriage or placental tearing at the time of birth, there is no danger to her
first Rh+ child. However, she does begin to produce anti-D antibodies upon
her first exposure to Rh+ foetal blood, although this does not occur
instantaneously. If she becomes pregnant again with a Rh+ foetus, her anti-
D antibodies can pass through the placenta and agglutinate the foetal RBCs.
Agglutinated RBCs haemolyse (release their Hb), and the baby is born with a
severe anaemia called haemolytic disease of the newborn (HDN), which may
kill the infant or leave brain damaged.

14. HDN is relatively easy to prevent, while very difficult to treat. A Rh-
mother is at risk of having a Rh+ baby if the baby’s father is Rh+.
As a result, it is now common to give immune globulin at 28-
32weeks gestation and at birth to any pregnancy involving a Rh-
mother and a Rh+ father. Immune globulin binds foetal RBC
antigens so that they cannot stimulate the mother’s immune
system to produce anti-D, hence preventing HDN.

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