Lecture 3 blood bank
THE ABO BLOOD GROUP
SYSTEM
By Dr. Dalia Galal Hamouda
Importance of the ABO system
Blood Group System is most important in blood transfusion
ABO Antibodies
•
Natural antibodies  found in the serum of people who lack the
antigen and antigenic stimulus is environmental  exposure occurs
from birth
•
Newborns  without ABO antibodies of their own; begin to produce
Ab with detectable titer at 6 months of age
•
Other characteristics of ABO antibodies:
1. IgM
2. Reacts at room temp. after an immediate spin
3. If ABO antibodies react with antigens in vivo, result is acute
hemolysis and possibly death
Why do individuals produce antibodies to
antigens they do not have?
• The "A“ and "B" antigens are also produced
by some other plants and microorganisms.
Thus, individuals who do not recognize one or
more of these antigens as "self" will produce
antibodies against the plant or microbial
antigens.
ABO grouping is required for all of the following individuals:
• Blood Donors-since it can be life threatening to give the wrong ABO group to the
patient.
• Transfusion recipients-since we need to know the donor blood is ABO
compatible.
• Transplant Candidates and Donors-ABO antigens are found in other tissues as
well. Therefore the transplant candidates and donors must be compatible.
• Prenatal Patients-To determine whether the mothers may have babies who are
suffering from ABO-HDN. It is also beneficial to know the ABO group should
she start hemorrhaging.
• Newborns (sometimes) If the baby is demonstrating symptoms of Hemolytic
Disease of the Newborn, the ABO group needs to be determined along with Rh
and others.
• Paternity testing Since the inheritance of the ABO Blood Group System is very
specific, this determines that the accused father is the father or not
ABO blood grouping system
According to the ABO blood
typing system there are four
different kinds of blood types:
A, B, AB or O (null).
AB0 blood grouping system
Blood group A
If you belong to the blood
group A, you have A
antigens on the surface of
your RBCs and B
antibodies (anti-B) in your
blood plasma.
Blood group B
If you belong to the blood
group B, you have B
antigens on the surface of
your RBCs and A
antibodies (anti-A) in your
blood plasma.
Blood group AB
If you belong to the blood group
AB, you have both A and B
antigens on the surface of your
RBCs and no A or B antibodies
at all in your blood plasma.
Blood group O
If you belong to the blood group O
(null), you have neither A or B
antigens on the surface of your RBCs
but you have both A and B antibodies
in your blood plasma.
ABO inheritance and genetics
• The ABO gene is autosomal (the gene is not on either sex
chromosomes)
• The ABO gene locus is located on the chromosome 9.
• A and B blood groups are dominant over the O blood group
• A and B group genes are co-dominant
• Each person has two copies of genes coding for their ABO blood
group (one maternal and one paternal in origin)
AUTOSOMAL
CHROMOSOME
A
The alleles for Blood
group are in the same
place on the
chromosome 9. However
the genes have a
different code giving the
different blood group
Sara
one alleles from Mustafa and one
from Sara.
B
Mustafa
What do co-dominant genes mean?
This meant that if a person inherited one A group gene and one
B group gene their red cells would possess both the A and B
blood group antigens.
These alleles were termed A ( which produced the A antigen ),
B (which produced the B antigen) and O (which was "non
functional"and produced no A or B antigen)
ABO BLOOD GROUP SYSTEM
The table shows the four ABO phenotypes ("blood groups")
present in the human population and the genotypes that give
rise to them.
Phenotype
Antigen on
RBCs
(blood group)
Natural
antibody
Genotype
A
A only
Anti-B
AA or AO
B
B only
Anti-A
BB or BO
AB
A and B
None
AB
O
None
Anti-A,
Anti-B
OO
ABO BLOOD GROUP SYSTEM
Example of determining offspring blood types from
known or suspected genotypes:
Genotype parent #1 (AO)
Genotype parent
#2 (AB)
A
O
A
AA
AO
B
AB
BO
Phenotypes of possible offsprings: A, AB, B
Possible Blood group Genotypes
Parent
Allele
A
A
B
O
AA
AB
AO
B
AB
BB
BO
O
AO
BO
OO
Antiserum
An antiserum is a purified, diluted and standardized solution containing known
antibody, which is used to know the presence or absence of antigen on cells.
Antiserum is named on the basis of the antibody it contains:
- Anti- A antiserum which contains anti- A antibody
- Anti- B antiserum which contains anti- B antibody
- Anti- AB antiserum, which contain both anti A and B antibodies.
- Anti –D antiserum which contains anti- D antibody
Sources of antisera
- Animal inoculation in which animals are inoculated by known antigen and the
resulting serum containing known antibody is standardized for use as antiserum.
- Serum is collected from an individual who has been synthesized to the antigen
through transfusion, pregnancy or injection.
Manifestation and Interpretation of
Antigen- Antibody reactions
The reactions (resulting from the combination of a red cell antigen with
its corresponding antibody) are agglutination and/ or haemolysis.
Hemolysis: is the break down or rupture of the red cell membrane by
specific antibody (hemolysin) through the activation of complement with
the release of hemoglobin and produce red color.
Agglutination: is the clumping of red cells when antigens on the red cell
membrane bind with their specific antibodies.it is the widely observed
phenomenon in blood grouping.
The agglutination of the red cells are called hemagglutination
The antigen is called agglutinogen
The antibody is called agglutinin.
Hemagglutination of red cells takes place in two stages:
First Stage:
•
red cell sensitization (when red cell become coated by antibodies)
•
Ag and Ab held by non-covalent interactions
Second Stage:
•
The physical agglutination or clumping of the sensitized red
cells (antibody attaches to antigen on more than one red cell)
•
formation of stable latticework  basis of visible reaction