Download 2-Blood Group Systems

Blood Group Systems
o How is blood classified?
Blood is classified according to the nature of the chemical substances
known as antigens or markers, which are microscopic substances found
on the surface of the red blood cells. They present on RBC as glycolipids
and as glycoproteins expressed on the surface of the RBC.
Antigens in the Human blood group:
1. Antigens in RBC.
2. Antigens in WBC.
3. Antigens in Platelet.
Antigens are controlled by chromosomes:
 Most of them are proteins (such as Rh, Duffy and Kidd), but some are
carbohydrates attached proteins (glycoproteins such as ABO, P and
Lewis).
 More than 254 different blood group antigens have been reported.
 Chromosome 9
 Chromosome 1
 Chromosome 19
ABO blood group
Rhesus blood group
Lewis blood group
Although there are many blood group systems with several sub-types, the
two best-known ways of classifying blood are the ABO group system and
the rhesus (Rh) type system.
1- ABO System:
At the turn of the 20th century, Karl Landsteiner discovered the ABO blood
group system, which is the most important one with respect to blood
transfusion and renal transplantation. The RBCs of each individual were
found either to lack or to have one or both of the two antigens, A and B. In
addition, the serum of each subject contained naturally occurring directly
agglutinating antibodies that recognized the antigens absent from their own
RBCs.
o
There are interesting variations in the frequencies of these blood
types in different human populations.
o
The ABO group is identified by a letter of the alphabet, so a person
can mainly belong to the A, B, AB or O blood group.
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ABO system Antigens:
There are three Antigens belong to this system, A, B and H.
Comments
o Serum from group A individuals contains naturally occurring anti-B
o Serum from group B individuals contains naturally occurring anti-A
o Serum from group A B individuals contains no Abs.
o Serum from group O individuals contains naturally occurring anti-A
and Anti-B
Serologists have defined two common subgroups of the A antigen.
Approximately 20% of group A and group AB individuals belong to group
A2 and group A2B, respectively, the remainder belonging to group A1 and
group A1B. These subgroups arise as a result of inheritance of either the A1
or A2 alleles.
o A2 red cells have fewer A antigen sites than A1 cells. In addition, the
number of A antigens on A1 RBCs is approximately five times more
than on A2 RBCs.
o The plasma of group A2 and group A2B individuals may also contain
anti-A1
o The H antigen content of red cells depends on the ABO group and
when assessed by agglutination reactions with anti-H, The strength of
reaction tends to be graded O > A2 > A2B > B > A1 > A1B.
o Other subgroups of A are occasionally found (e.g., A3, Ax) that result
from mutant forms.
Blood Group Antibodies:
In vitro characteristics of the ABO Ab:
1. Naturally Occurring Antibodies " ABO antibodies, in the absence of
the corresponding antigens, appear during the first few months after birth,
probably as a result of exposure to ABH antigen-like substances in the
diet or the environment (i.e., they are “naturally occurring”)
2. Immunoglobulin class IgM ''complete'' that directly agglutinate the
appropriate antigen-positive RBCs.
3. Optimal technique RT or below ''cold reacting''.
4. Neutralization Saliva from A secretors
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5. Complement binding Yes '' very actively'' some hemolytic (rare in A2)
6. Do not cross the placenta
Blood
Group
Antigens on
RBCs
Antibodies 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
Secretors and Nonsecretors
People make A, B, and H secretor substances. The substances appear as Ags
in the body fluids.
The ability to secrete A, B, and H substances in water-soluble form is
controlled by FUT2 (gene). Secretors have H substance in the saliva and
other body fluids together with A substances, B substances, or both,
depending on their blood group.
Can be homozygous Se Se - Produce ABH substances
Heterozygous Se se - Produce ABH substances
Allelemorphic se se - No production of ABH substances.
Only traces of these substances are present in the secretions of nonsecretors,
although the antigens are expressed normally on their red cells and other
tissues.
Inheritance of ABO
• ABO & RH genes are not linked
• Genotype: Sum of the genes.
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• Phenotypes: product of the genes.
Allele from
the mother
Allele from
the father
Genotype of
offspring
Blood types of
offspring
A
A
AA
A
A
B
AB
AB
A
O
AO
A
B
A
AB
AB
B
B
BB
B
B
O
BO
B
O
O
OO
O
Universal Donor and Recipient
1. Universal Donor
• Group O
– Carries no A or B antigens
– Packed and processed units have little antibody
2. Universal Recipient
• Group AB
– Patient has no anti-A or anti-B present
– Cannot lyse any transfused cells
– Beware: other
– antibodies may be present
ABO mismatched transfusions:
– Rare.
– May be life threatening.
– Can be caused by technical or clerical error.
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– Intravascular haemolysis.
– More severe in group O patients.
2- Other blood groups
Several other blood group antigens have been identified in humans. Some
examples: MN, Duffy, Lewis, Kell.
They, too, may sometimes cause


transfusion reactions and even
hemolytic disease of the newborn
in cases where there is no ABO or Rh incompatibility.
Lewis Blood Group System
Le
The 7th blood groud.
ABH and Lewis Ag are much related together biochemically. Both have the
same basic structure (15 Amino Acids), they are glycoproteins.
Lewis Ag:
Soluble Ag
Production governed by two genes Le a & Le b
At birth, there is no Lewis Ag.
It takes 3-4 years for the Ags to become strong on the surface of the RBCs.
Lewis Ab:
1. Anti Le a
2. Anti Le b
Agglutinate blood in saline (IgM), work best at 20oC, and fix the
complement.
Do not cause HDN of new born because:
1- Ag not developed yet.
2- IgM, can not cross the placenta.
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Bombay Phenotype
It is an abnormal blood group. Discovered in Bombay in 1952.
It is important to be cautious in predicting the ABO blood type of children
based on the phenotypes of their parents. This is due to the fact that a third
antigen (H) on the surface of red cells can prevent the expected ABO blood
type from occurring.
Normally, if an A blood type mother has an O type child; the father is
expected to be type O or at least to carry the O allele (OO, AO, or BO
genotype).
The child has inherited an O allele from both parents. However, an O blood
type child can also be born to parents who do not have the O allele if a
recessive form of the allele for the H antigen also is inherited from both
parents.
The H antigen is a precursor to the A and B antigens. For instance, the B
allele must be present to produce the B enzyme that modifies the H antigen
to become the B antigen. It is the same for the A allele. However, if only
recessive alleles for the H antigen are inherited (hh), as in the case above,
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the H antigen will not be produced. Subsequently, the A and B antigens also
will not be produced. The result is an O phenotype by default since a lack of
A and B antigens is the O type.
This seemingly impossible phenotype result has been referred to as a
Bombay phenotype because it was first described in that Indian city.
3- Rhesus (Rh) blood grouping system
Antigens:
 This is one of the most important blood grouping systems.
 Named because it was first discovered in rhesus monkeys
 In 1940 Landsteiner and Wiener showed that antibodies produced
against the rhesus monkey RBCs agglutinated RBCs of 85% of a
human population.
 The antibodies were directed against a molecule called the rhesus (Rh)
antigen, and individuals possessing it were called Rh positive.
 Natural antibodies against the Rh antigens do not occur.
 The gene product is identified as the RhD antigen or D antigen.
 Rh system is very complex, and our present understanding is based on
the Fisher system.
 Three genes making up Rhesus antigens: C, D, and E, found on
chromosome 1, the D Ag is the most important one.
 There are two possible alleles at each locus: c or C; d or D; and e or E.
 One haplotype consisting of c/C, d/D, e/E is inherited from each
parent, and the resulting Rhesus type of the individual depends on
their inherited genotype, this will lead to the following genotypes CDe,
cDE, cde, cDe, Cde, cdE, CdE, cde.
 If an individual's Rh genotype contains at least one of the C, D, E
antigens, they are Rhesus positive.
 Only individuals with the genotype cde/cde (rr) are Rhesus negative.
 The most common Rh antibody is anti-D, but it is possible to form
antibodies to c, C, e, and E as well, and to form combinations of
antibodies. There is no anti-d.
Other Rh Ags:
1- Cw Ag:
Very rare, and can causes HDN, and HTR.
2- G Ag.
3- Du Ag: it is an important Ag, which must be regarded as D Ag. in
Nigeria, 8% of the people type as D-, are Du. Very strong Anti-D Ab
should be used to detect Du Ag.
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Antibodies to the Rh system:
No naturally occurring.
All the Ab re immune IgG Abs.
All the five Ags will produce immune Abs when given to people not
from the same Rh group.
D>c>E>e>C
Abs can cause HDN and HTR.
In any of the 4 ABO groups, a person can be Rh positive or Rh negative,
meaning that a person’s blood can be classified as one of 8 possible types
(O+, O-, A+, A-, B+, B-, AB+, AB-).
Discovered in 1901.
ABO system is very common.
Rh system is common
Other is occasional and rare.
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