BLOOD GROUPS
-I
Ms Veena Shriram
GENETICS OF BLOOD TYPES
 Our
blood type is established before we are BORN,
by specific GENES inherited from our parents.
 We
inherit one gene from our MOTHER and one
from our FATHER.
 These
genes determine our blood type by causing
proteins called AGGLUTINOGENS to exist on the
surface of all of our red blood cells.
 Competencies - the students should achieve
at the end of this topic: he should be able to

Describe and Classify different blood groups.

Define Landsteiner’s laws.

Discuss the clinical importance of blood grouping.

Describe Rh incompatibility.

Describe hemolytic diseases due to Rh
incompatibility.

Erythroblastosis fetalis; its treatment and
SYNOPSIS
Introduction
 The ABO System
 Inheritance
 Antigens & Agglutinogens of blood groups
 Nature of agglutinins (Antibodies)
 Landstiners law
 Compatibility between blood groups
 Agglutination (Clumping)
 Crossmatching
 Possible complications of blood transfusions
 HDN
 Fate of the transfusion reactions

The ABO System:

Discovered in 1901 by Dr. Karl
Landsteiner, won Nobel prize in
medicine

The A & B antigens inherited as
mendelian dominants

4 Main Phenotypes (A, B, AB, O)

ABO gene on chromosome 9

Different people had different antigenic and
immune properties hence blood transfusion to a
person
belonging
to
different
blood
group:
mismatching lead to severe reactions in the body.
o
Several hundred antigens present on the surface of
RBCs.

Most of these antigens do not cause major reactions,
∴ called minor blood groups e.g. MNS, P, Lutheran,
Kell, Kidd, Lewis, Dufy, Diego and many others.
DIFFERENT BLOOD GROUP
SYSTEMS

ABO

Kell system

Rh

Duffy system

MNS

Kidd system

Lewis

Lutheran (Lu)

Ss

P
system

Ii system
 These are mainly useful for studying inheritance of genes.
ABO SYSTEM:

ANTIGEN: Any foreign invading substance which can evoke an
immune response in the body. Antigens of blood groups are
macromolecules, which occur on the surfaces of the red
blood cells and on different body cells called:
AGGLUTINOGENS: complex oligosaccharides present on the
surface of the RBC membrane. viruses and in bacteria, too
- these antigens can be determined from the third month
of foetal life until the end of our lives
- production of antigens are controlled by the genes
inherited from both of the parents
Classification of blood groups:
Depending on the presence or absence of
agglutinogen on the surface of RBC membrane,
blood groups are classified as follows:
Agglutinogen Blood Group
% (Indians*)
A
B
A&B
A
B
AB
41
09
03
(22)
(33)
(7)
-
O
47
(37)
*A Contribution to the Physical Anthropology & Population Genetics L.Beckman:revised by bloodBook.com 2008.

Blood Group A is further classified as A1 and A2 (On addition
of kulith extract, agglutination seen with A1)

In 80% people agglutinogens are present in various secretions
(gastric, salivary) hence they are called secretors.

ANTIBODIES: are substances formed in response to an
antigen.

AGGLUTININS: are specific antibodies, naturally found in
the plasma ,which have the ability to bind to a specific
agglutinogen e.g. antiA, antiB. They are formed in the plasma
in response to various antigens entering the body via food,
inhalation, bacteria etc.
Blood group Agglutinogen
A
A
B
B
AB
A,B
O
---
Agglutinin
AntiB
AntiA
--AntiA, AntiB
Q: If the Ag A is present on the Red cell, why is Anti A not
produced? Why is Anti B being formed in the plasma?
A: Ag A is present at birth and is recognized as self antigen hence
antibodies Anti A are not produced in response to antigen A entering
the body. However Anti B is produced in the plasma in response to
various antigens entering plasma via food, inhalation, bacteria etc.
Titer of Agglutinins at different ages:
At birth, concentration is zero starts at 2 to 8 months,
maximum at 8 to 10yrs, declines throughout life.
WHAT ARE BLOOD TYPES?
There are 3 alleles or genes for blood
type: A, B, & O. Since we have 2 genes,
there are 6 possible combinations.
Blood Types
AA or AO = Type A
BB or BO = Type B
OO = Type O
AB = Type AB
http://learn.genetics.utah.edu/units/basics/blood/types.cfm
Genotype
OO
Phenotype
/blood group
O
A1
A2
Agglutinogen
on RBC
-
A1
A2
A 1A 1 / A 2 A 2 / A 1B
A1A2 / A2O
A 1O
Agglutinin in Anti-A [α] Anti-B Anti-B
Anti-B [β] [β]
[β]
plasma
A1 B
A2 B
BB /
OB
A2B
B
A1 & B A2 & B
-
-
B
Anti-A
[α]
THE DIFFERENCE BETWEEN
IgM & IgG ANTIBODIES
IgG
IgM
ANTIGENS
GROUPS:

&
AGGLUTINOGENS
OF
BLOOD
Antigens of blood groups are macromolecules, occur on
the surfaces of red blood cells & on different body cells
 Structures
of
surface
–
polysaccharides,
glycoproteins, lipoproteins
 These particles of cells can be found in plants, in
vertebrates, in viruses and in bacteria, too
 These antigens can be determined from the third
month of fetal life until the end of our lives
 Production of antigens are controlled by the genes
inherited from both of the parents
 At least 15 commonly occurring antigens are able
to cause blood transfusion reactions
SYSTEM:

The separation depends on the genetically determined
polysaccharide groups of the membrane glycoproteins

Two allelomorphic genes determine the O-A-B blood
groups. The basic epitop (i.e. the group of antigens, which
determine antigen specificity) is the H-antigen = Bld grp 0.
Two different polysaccharide rests are connected to this
antigen. A & B antigen specificities are determined by
these polysaccharide chains.

The antigens of the O-A-B systemare present in the
living world – after birth in the alimentary & they
produce an immune response if this baby doesn’t have
this antigen. They are
antibodies of IgM type
natural
anti-A,
anti-B
ANTIGENS OF THE ABO SYSTEM





An H gene codes for a fucose transferase that puts a
fucose on the end of these glycolipids or glycoproteins,
forming the H antigen that is usually present in
individuals of all blood types.
Individuals who are type A have a gene which codes
for a transferase that catalyzes placement of a
terminal N-acetylgalactosamine on the H antigen.
Individuals who are type B have a gene which codes
for a transferase that places a terminal galactose.
Individuals who are type AB have both transferases.
Individuals who are type O have neither, so the H
antigen persists.
THE ABO ANTIGENS

Added to Proteins or Lipids in Red Cells

Substrate Molecule is H (fucose)

A antigen is N-acetyl-galactosamine (NAcG)

B antigen is galactose (Gal)

A and B genes code for transferase enzymes
ANTIGENS OF THE ABO SYSTEM ON THE
SURFACE OF RED BLOOD CELLS:
H antigen
A antigen
B antigen
G
F
F
G
F
G
G
G
G
G
G
G
G
G
G
G
C
C
C
Ceramide
G
G Galactose
G
C
G
Glucose
F
Fucose
N-acetylgalactosamine

Subgroups of blood types A and B have been
described.

The most important being A1 and A2.

However, the difference between A1 and A2
appears to be quantitative;

Each A1 cell has about 1,000,000 copies of the A
antigen on its surface,

And each A2 cell has about 250,000.
Nature of agglutinins:
LANDSTEINER’S LAW:
States that

1)
if an agglutinogen is present on the RBC
membrane, then the corresponding agglutinin must be
absent in the plasma.

2) if an agglutinogen is absent on the RBC
membrane, then the corresponding agglutinin must be
present in the plasma.
ABO system follows both parts of Landsteiner’s law.

Compatibility between blood groups:
Major reaction-between Donor’s cells & recipient’s plasma
 Minor reaction-Between Donor’s plasma & Recipient’s cells

Donor’s
group
A[A- β]
B [B-α]
AB[AB-nil]
O [nil-αβ]
Recipient’s group
A[A-β] B [B-α] AB[AB-nil] O [nil-αβ]
√
χ
χ
√
χ
√
χ
√
√
√
√
√
χ
χ
χ
√
Blood group O - Universal Donor & Blood group AB - Universal Recipient
Que:
Ans:
Que:
Ans:
Can Blood Group A be given to AB?
Yes. Since AB has no natural agglutinins, donor cells are safe
and anti B of donor serum gets diluted in the recipients plasma.
Can Blood Group A be Given to O?
No. Because donor cells (AgA ) get agglutinated by recipients anti- A.

AGGLUTINATION:

When a specific agglutinogen e.g. AgA comes in contact with
a specific agglutinin e.g. Anti A, there occurs an antigen
antibody reaction in the form of agglutination.

Anti A has 10 binding sites (IgM) hence potentially 10 RBC’s
having agglutinogen A can bind to it.

Agglutination can be between Donor RBC’s (E.g. Gr. A RBCAgA) and Recipients plasma agglutinins (Gr. B, AntiA) or
between Donor’s plasma agglutinins (Gr.A, antiB) and
recipients RBC (Gr.B, AgB).

Que.: Donor RBC’s having AgA are agglutinated by the recipients plasma
agglutinins AntiA. What happens to recipients RBC having AgB? Do they
agglutinate due to donors agglunins AntiB?

Ans: No. Because the donors plasma is diluted in the recipients plasma
hence the antibodies are diluted, hence fail to agglutinate the recipients RBC.
Red cell agglutination in incompatible plasma.
CROSSMATCHING:

Major Matching: Suspension of donor
erythrocytes is mixed with recipient’s serum.

Minor Matching: Suspension of recipient’s
erythrocytes is mixed with donor’s serum
In both cases if there is no agglutination, blood is
perfectly compatible
Cross Matching (Major)
Donor’s RBCs
Blood samples to be
typed is added to the
drops of serum
Group A
Group B
Group AB
Agglutination or
clumping of RBCs
Group O
Recipient’s plasma
Serum containing
Anti-A
Anti-B
antibodies
antibodies
Possible complications of blood transfusions
1. Incompatibility reactions
Antigens on donor’s RBC + Antibodies in recipient’s plasma
RBC Agglutination
Clumps
I/V haemolysis
release of Hb
Haemoglobinaemia and Jaundice
Renal failure
‘DEATH’
may block
blood vessels
2. Fever - due to the presence of antibodies against
transfused WBCs and platelets
3. Allergic reactions - asthma
4. Circulatory overload
5. Iron overload
6. Air embolism - air can go into the circulation
7. Transmission of diseases - Malaria, hepatitis B, AIDS,
Syphilis
To avoid these complications “Autologous
transfusion” can be done.
Haemolytic disease of the newborn (HDN)
* ABO Incompatibility – common but mild
* Rh Incompatibility
FATE OF THE TRANSFUSION






REACTIONS:
Agglutinated cells block small vessels
Phagocytosis by WBC,s or they burst in
the spleen or lungs leading to release of Hb
Hb is then converted to bilirubin –jaundice
If the titer of antibodies is very high,
activation of the complement system
Acute haemolysis ,released Hb blocks
renal tubules -renal shutdown
Determination of Blood Groups:
Antiserum A
Antiserum B
√
×
√
×
×
√
√
×
Blood Group
A
B
AB
O