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The Blood Group Systems
Dr. Yogendra Vijay
Resident doctor
SMS Medical college,Jaipur
(Rajasthan)
•The blood group you belong to depends on what you have inherited from your parents.
• There are more than 20 genetically determined blood group systems known today
• The AB0 and Rhesus (Rh) systems are the most important ones used for blood transfusions.
• Not all blood groups are compatible with each other. Mixing incompatible blood groups leads to blood clumping or agglutination, which is dangerous for individuals.
Blood group AIf you belong to the blood group A, you have A antigens on the surface of your RBCs and B antibodies in your blood plasma.
Blood group BIf you belong to the blood group B, you have B antigens on the surface of your RBCs and A antibodies in your blood plasma.
AB0 blood grouping system
Blood group ABIf 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 OIf you belong to the blood group O, 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.
• 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.
• These antibodies will also react with human antigens of the same kind whether introduced via a blood transfusion or a tissue graft.
Significance of ABO Group
ABO mismatched transfusions:
Rare
May be life threatening
Can be caused by technical or clerical error
Intravascular haemolysis
More severe in group O patients
7
• The ABO gene is autosomal (the gene is not on either sex
chromosomes)
• The ABO gene locus is located on the chromosome 9.
• Each person has two copies of genes coding for their ABO blood
group (one maternal and one paternal in origin)
• A and B blood groups are dominant over the O blood group
• A and B group genes are co-dominant
ABO inheritance and genetics
Principles of Heredity
Antigens and enzymes are genetically controlled
Genes: responsible for transfer of hereditable material
Genes are found on chromosomes, which are found in the nucleus of every cell
Human Cells contain 46 chromosomes with the exception of the egg and sperm, which contain only 23.
23 of these chromosomes are inherited from mother
23 of these chromosomes are inherited from father
Genes Come in Pairs
The position a gene occupies on a chromosome is called a locus.
Genes for the same trait are located at the same locus on both the mother and the father’s chromosomes.
Alternative forms of genes that influence a given characteristic are called alleles.
Father: allele for brown eyes
Mother: allele for blue eyes
Blood Types are Genetic
A and B Blood Types are Dominant
Dominant: Characteristic is shown
Blood Type O is Recessive
Recessive: Characteristic is hidden
Recessive characteristics only appear when both alleles are recessive
Homozygous recessive OO
Phenotype V. Genotype
Phenotype: individual’s outward characteristics
Genotype: individual’s pair of allele genes together
Example:
Phenotype Genotype
Type B Blood Could be BO or
BB depending
on parents
Important Parts for Forensic Science
Red Blood Cells—because of their importance in blood typing
Serum—because of its’ importance in carrying antibodies
ABO and H Antigen Genetics
Genes at three separate loci control the occurrence and
location of ABO antigens
The presence or absence of the A, B, and H antigens is
controlled by the H and ABO genes
Location
The presence or absence of the ABH antigens on the red
blood cell membrane is controlled by the H gene
The presence or absence of the ABH antigens in
secretions is indirectly controlled by the Se gene
ABO Antigen Genetics
H gene – H and h alleles (h is an amorph)
Se gene – Se and se alleles (se is an amorph)
ABO genes – A, B and O alleles
H Antigen
The H gene codes for an enzyme that adds the sugar
fucose to the terminal sugar of a precursor substance
(PS)
The precursor substance (proteins and lipids) is formed
on an oligosaccharide chain (the basic structure)
RBC Precursor Structure
Glucose
Galactose
N-acetylglucosamine
Galactose
Precursor
Substance
(stays the
same)
RBC
Formation of the H antigen
Glucose
Galactose
N-acetylglucosamine
Galactose
H antigen
RBC
Fucose
H antigen
The H antigen is the foundation upon which A and B
antigens are built
A and B genes code for enzymes that add an
immunodominant sugar to the H antigen
Immunodominant sugars are present at the terminal ends
of the chains and confer the ABO antigen specificity
A and B Antigen
The “A” gene codes for an enzyme (transferase) that adds N-acetylgalactosamine to the terminal sugar of the H antigen
N-acetylgalactosaminyltransferase
The “B” gene codes for an enzyme that adds D-galactose to the terminal sugar of the H antigen
D-galactosyltransferase
Formation of the A antigen
Glucose
Galactose
N-acetylglucosamine
Galactose
RBC
FucoseN-acetylgalactosamine
Formation of the B antigen
Glucose
Galactose
N-acetylglucosamine
Galactose
RBC
FucoseGalactose
Genetics
The H antigen is found on the RBC when you have the
Hh or HH genotype, but NOT from the hh genotype
The A antigen is found on the RBC when you have the
Hh, HH, and A/A, A/O, or A/B genotypes
The B antigen is found on the RBC when you have the
Hh, HH, and B/B, B/O, or A/B genotypes
Group O Group A
Many H
antigen sites
Fewer
H antigen
sites
A
A A
AA
Most of the H antigen sites in a
Group A individual have been
converted to the A antigen
ABO Antigens in Secretions
Secretions include body fluids like plasma, saliva,
synovial fluid, etc
Blood Group Substances are soluble antigens (A, B, and
H) that can be found in the secretions. This is
controlled by the H and Se genes
Secretor Status
The secretor gene consists of 2 alleles (Se and se)
The Se gene is responsible for the expression of the H
antigen on glycoprotein structures located in body
secretions
If the Se allele is inherited as SeSe or Sese, the person is
called a “secretor”
80% of the population are secretors
Secretors
Secretors express soluble forms of the H antigen in secretions that can then be converted to A or B antigens (by the transferases)
Individuals who inherit the sese gene are called “nonsecretors”
The se allele is an amorph (nothing expressed)
sese individuals do not convert antigen precursors to H antigen and has neither soluble H antigen nor soluble A or B antigens in body fluids
Secretor Status Summary
The Se gene codes for the presence of the H antigen in
secretions, therefore the presence of A and/or B
antigens in the secretions is contingent on the
inheritance of the Se gene and the H gene
Se gene (SeSe
or Sese)
H antigen in
secretions
A antigen
B antigen
se gene (sese) No antigens secreted
in saliva or other
body fluids
and/or
ABO Subgroups
ABO subgroups differ in the amount of antigen present on the red blood cell membrane
Subgroups have less antigen
Subgroups are the result of less effective enzymes. They are not as efficient in converting H antigens to A or B antigens (fewer antigens are present on the RBC)
Subgroups of A are more common than subgroups of B
Subgroups of A
The 2 principle subgroups of A are: A1 and A2
Both react strongly with reagent anti-A
To distinguish A1 from A2 red cells, the lectin Dolichos
biflorus is used (anti-A1)
80% of group A or AB individuals are subgroup A1
20% are A2 and A2B
A2 Phenotype
Why is the A2 phenotype important?
A2 and A2B individuals may produce an anti-A1
This may cause discrepancies when a crossmatch is done (incompatibility)
What’s the difference between the A1 and A2 antigen?
It’s quantitative
The A2 gene doesn’t convert the H to A very well
The result is fewer A2 antigen sites compared to the many A1 antigen sites
A1 and A2 Subgroups*
Anti-A
antisera
Anti-A1
antisera
Anti-H
lectin
ABO
antibodies
in serum
# of
antigen
sites per
RBC
A14+ 4+ 0 Anti-B 900 x103
A24+ 0 3+ Anti-B &
anti-A1
250 x103
*Adapted from Flynn, J. (1998). Essentials of Immunohematology
Other A subgroups
There are other additional subgroups of A
Aint (intermediate), A3, Ax, Am, Aend, Ael, Abantu
A3 red cells cause mixed field agglutination when
polyclonal anti-A or anti-A,B is used
Mixed field agglutination appears as small agglutinates
with a background of unagglutinated RBCs
They may contain anti-A1
B Subgroups
B subgroups occur less than A subgroups
B subgroups are differentiated by the type of reaction
with anti-B, anti-A,B, and anti-H
B3, Bx, Bm, and Bel
ABO Blood Group:ABO Antibodies
Landsteiner’s Rule:
Normal, Healthy
individuals possess
ABO antibodies to
the ABO antigen
absent from their
RBCs
Blood Group Systems
Most blood group systems (ABO and others) are made up of:
An antigen on a red cell and the absence of it’s corresponding antibody in the serum (if you’re A, you don’t have anti-A)
If you do NOT have a particular antigen on your red cells then it is possible (when exposed to foreign RBCs) to illicit an immune response that results in the production of the antibody specific for the missing antigen
ABO
The ABO Blood Group System
does NOT require the presence of
a foreign red blood cell for the
production of ABO antibodies
ABO antibodies are “non-red
blood cell stimulated” probably
from environmental exposure and
are referred to as “expected
antibodies”
Anti-A1
Group O and B individuals contain
anti-A in their serum
However, the anti-A can be
separated into different
components: anti-A and anti-A1
Anti-A1 only agglutinates the A1
antigen, not the A2 antigen
There is no anti-A2.
Anti-A,B
Found in the serum of group O
individuals
Reacts with A, B, and AB cells
Predominately IgG, with small
portions being IgM
Anti-A,B is one antibody, it is
not a mixture of anti-A and
anti-B antibodies
ABO antibodies
IgM is the predominant antibody in Group
A and Group B individuals
Anti-A
Anti-B
IgG (with some IgM) is the predominant
antibody in Group O individuals
Anti-A,B (with some anti-A and anti-B)
ABO antibody facts
Reactions phase: Room
temperature
Complement can be activated with
ABO antibodies (mostly IgM, some
IgG)
High titer: react strongly (4+)
ABO Antibodies
Usually present within the first 3-6
months of life
Stable by ages 5-6 years
Decline in older age
Newborns may passively acquire maternal
antibodies (IgG crosses placenta)
Reverse grouping (with serum) should
not be performed on newborns or cord
blood
Paternity Tests
No blood group can be present in a child without being present in one of the parents
Paternity tests can be resolved in this way unless disputed fathers have the same blood type
Paternity tests can also be determined by using DNA testing
Blood as Evidence
Blood typing not so useful anymore because of DNA technology
Scientists can now characterize biological evidence by
selecting regions of our DNA
AUTOSOMAL CHROMOSOME
Dad
Mom
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
A B
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)
What do co-dominant genes mean?
Parent
Allele
A B O
A
B
O
Possible Blood group Genotypes
Parent
Allele
A B O
A AA AB AO
B AB BB BO
O AO BO OO
Possible Blood group Genotypes
The ABO blood groups
• The most important in assuring a safe blood transfusion.
• The table shows the four ABO phenotypes ("blood groups") present
in the human population and the genotypes that give rise to them.
Blood
Group
Antigens
on RBCsAntibodies in Serum Genotypes
A A Anti-B AA or AO
B B Anti-A BB or BO
AB A and B Neither AB
O Neither Anti-A and anti-B OO
The ABO Blood Group System
Laboratory Determination of the
ABO System
METHODS OF ABO BLOOD GROUPING
1.SLIDE METHOD
2.TUBE METHOD
3.GEL SYSTEM
4.MICROPLATE TECHNIQUE
5.GLASS MICROBEAD METHOD
6.GALILEO METHOD
Several methods for testing the ABO group of an individual exist. The most common method is:
Serology: This is a direct detection of the ABO antigens. It is the main method used in blood transfusion centres and hospital blood banks.
This form of testing involves two components:
a) Antibodies that are specific at detecting a particular ABO antigen on RBCs.
b) Cells that are of a known ABO group that are agglutinated by the naturally occurring antibodies in the person's serum.
• Illustration of the forward and reverse grouping reaction patterns of the ABO groups using a blood group tile
Blood Group
Antigens Antibodies Can give blood to
Can receive
blood from
AB
A
B
O
Blood Group
Antigens Antibodies Can give blood to
Can receive
blood from
AB A and B None AB AB, A, B, O
A A B A and AB A and O
B B A B and AB B and O
O None A and B AB, A, B, O O