ABO blood system

7/29/2019 ABO blood system

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ABO BLOOD GROUP

DR. MOHAMMED H SAIEM ALDAHR

Faculty of Applied Medical Sciences

BLOOD BANK

MEDICAL TECNOLOGY

KAAU


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ABO BLOOD GROUP

History1. Landsteiners discovered the ABO Blood Group

System in 1901

2. He and five co-workers began mixing each others redblood cells and serum together and accidentallyperformed the first forward and reverse ABOgroupings.

3. Landsteiners Rule: If an antigen (Ag) is present on apatients red blood cells the corresponding antibody (Ab) willNOTbe present in the patients plasma, under normalconditions.


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ABO BLOOD GROUP

Importance of ABO

There are two principles

1-almost all normal healthy individuals above 3-6months of age have naturally occurring Abs to the

ABO Ags that they lack

These Abs termed naturally occurring because they

were thought to arise without antigenic stimulation


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ABO BLOOD GROUP

Importance of ABO

2- These naturally occurring Abs are mostlyIgM class.That means that, they are Abs capable of agglutinatingsaline/ low protein suspended red cell withoutenhancement and may activate complement cascade.


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Major ABO Blood Group

Forward blood grouping using anti-sera and red blood cells

ABO

Group

AntigenPresent

AntigenMissing

AntibodyPresent

A A B Anti-B

B B A Anti-A

O None A and B Anti-A&B

AB A and B None NoneIf an antigen (Ag) is present on a patients red blood cellsthe corresponding antibody (Ab) will NOT be present in thepatients plasma, under normal conditions.


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ABO BLOOD GROUP (Forward blood grouping )Determination ofABO antigens found on patient red blood cells using reagent anti-sera. Serum from BG Baggl ARBCs, that an Ab to AAg was present in Grp B serum, serum fromAagg Grp B RBCs

Patient Red Cells Tested With

InterpretationAnti-BAnti-APatient

O001

A04+2

B4+03

AB4+4+4


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Reverse Grouping (Confirmatory grouping)

Patient Serum Tested With reagent red blood cellsSerum from GRP O individual aggl bothAand B cells indicate the presence ofAbs to bothAand B in group O serum

InterpretationB CellsA1 CellsPatient

O4+4+1

A4+02

B04+3

AB004


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FORWARD & REVERSE ABO BLOODGROUPING

Reaction of Cells TestedWith

Reaction of SerumTested Against ABO

Group

Anti-A Anti-B A1 Cells B Cells

1 0 0 + + O

2 + 0 0 + A

3 0 + + 0 B

4 + + 0 0 AB


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ABO INHERITANCE

T2Dad =A/O

and

Mom = B/O

Mom

B O

DadA A/B A/O

O O/B O/O


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ABO groups of the offspring from the various possible ABOmating

Phenotypes Genotype offspringAxA AAxAA A (AA)

AAxAO A (AA or AO)

AOxAO A (AA or AO),O(OO)

BxB BBxBO B (BB or BO)

AxAB AAxAB AB (AB) or A (AA)

AOxAB AB (AB), A (AA, AO), B(BO)


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Inheritance

Definition

Isoagglutinins: are defined as antibodies that agglutinateblood cells of some individuals of the same species

Glycosyltransferases: are enzyme that facilitate thetransfer of carbohydrate (sugar) molecules ontocarbohydrate precursor molecules

Immunodominant sugar: is the sugar molecule thatcomplete the antigenic determinant when combined withthe precursor substance


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ABH ANTIGEN

The inheritance of the ABO blood group was

demonstrated that each individual inherits one ABO gene

from each parent and these two genes determine which Agsare present on RBCs membrane

One position or Locus, on each chromosome number

nine is occupied by an A, B, or an O gene


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ABH ANTIGEN

ALocus termed H and the final product of the genes atthat locus, H antigen, was necessary for the expression ofnormalABO antigens (Allele: any alternate form of a gene that can occupy a givenchromosomal location (locus).

ABHAgs of the RBC membrane are found partly asglycolipids,but primarily as glycoproteins. It may alsooccur in the secretion as glycoproteins.


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ABH Antigens

Ags belonging toABH blood group system are present onRBCs and other body cells and body fluids.

The presence of A,B, and O Ags on RBCs depends uponthe allelic genes, A,B, and O

An Hgenes at a separate locus codes for the precursorsubstance on which theAand B gene products act

The products of theA and B genes are enzymes that act asa specific transferases


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ABH Antigens

H gene products is an enzyme that produce H substance

The O gene is a silent allele

It does not alter the structure ofH substance.


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Formation of A1B& H Antigen

TheABO genesdo not code for the production ofABOantigens, BUT rather produce specific glycosyltransferases

ABO produces a specific glycosyl transferases that add

sugars to a basic precursor substance on the RBCs

A donor nucleotide derivative supplies the sugar thatconfers (gives) ABO specificity (is the sugar molecule thatcomplete the antigenic determinant when combined with

the precursor substance )

The formation ofABH antigens results from theinteraction of ABO genes with several other separate,

independent blood groups.


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Formation of A1B& H Antigen

The inheritance of at least one H gene (HH or Hh) elicits(obtain) the production of an enzyme called, -2-L-Fucosyl transferase, which transfers the sugar from the

Guanosine diphosphate L-fucose (GDP-Fuc) donornucleotide to the terminal galactose of the precursorchain.

The H substance must be formed for the other sugars to

be attached in response to an inherited A and /or B genes


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ABH Ag

There are two potential precursors substance (PS) both arecomprised of identical sugar (galactos-N- acetylgluctosamin - galactose -glucose) but different in linkage.

Type I PS has a terminal galactose (Gal) linked to asubterminal N acetylgucoseamine (GlcNAc) in 1-3linkage

Type II PS, has the same sugar combine in 1-4 linkage

ABH Ags on RBCs are derived from Type II chains.


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ABO Genetics

Genes at three separate loci control the occurrence andlocation of A and B antigens

1. Hh genes Hand h alleles

Hallele codes for a fucosyltransferase enzyme thatadds a fucose on Type 2 chains (primarily) to form theH antigen onto which A and B antigens are built onred blood cells.

h allele is a silent allele (amorph)


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ABO Genetics

A, B and H antigens are built

on oligosaccharide chains of 4types. The most commonforms are Type 1 and Type 2.

Type 1: #1 carbon of Gal is

attached to the #3 carbon ofGlcNAc.

Type 2: #1 carbon of Gal isattached to the #4 carbon of

GlcNAc.


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ABO Genetics

2- Se genes

Se and se allelesSe allele codes for a fucosyltransferase enzyme that

adds fuscos onto Type 1 chains (primarily) insecretory glands. Controls expression of H antigens in

secretions (i.e. saliva, body fluids, etc.) se allele is an a morph

3. ABO genes A,B and O alleles

A and Balleles code for (glycosyltransferase)afucosyltransferase enzymes that add a sugar onto Hantigens to produce A and B antigens

O allele does not code a functional enzyme


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ABO Genetics

1. Occurance

a. The presence or absence of theABH antigens onthe red blood cell membrane is controlled by theHgene

b. Presence or absence of theABH antigens insecretions is indirectly controlled by theSe genes.


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ABO Genetics

1. Hh gene Hand halleles (h is an a morph)

2. Se gene Se and sealleles (se is an amorph)

3. ABO genes A, B and Oalleles

1. Controls presence of H,A, and B antigens onboth RBCs and in

Secretions

2. Controls presence of Hantigen in the secretions

3. Inherit 1 gene from eachparent that codes for anenzyme that adds asugar to the H antigen


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H gene acts on

a Precursor

substance(PS)*

by addingFucose

H Antigen

*PS = oligosaccharide chain

attached to either glycosphingo-

lipid, Type 2 chain (on RBC) or

glycoprotein, Type 1 chain (in

secretions)

TheHgene codes for an enzyme (fucosylytranferase) that adds a

Fucose to the terminal sugar of a Precursor Substance (PS*).The biochemical structure below constitutes the H Antigen. (hgene is an amorph.)


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ABO Genetics

H antigen is the foundation upon which A and Bantigens are built.A andB genes code for

enzymes that add an immunodominant sugar tothe H antigen.


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Formation of theA Antigen

TheA gene codes

for an enzyme that

adds GalNAc(N-Acetyl-D

galactosamine)

to the terminal

sugar of theH Antigen. The biochemical structure

constitutes the A antigen.


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Formation of theB Antigen

Bgene codes for an

enzyme that adds

D-Galactoseto the terminal sugar

of the H Antigen.

The biochemical structure

constitutes theB Antigen.


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The H antigen is found on

the RBCs when there is anHh

orHHgenotypes but NOT

with the hh genotype.

The A antigen is found on

the RBCs when there isHh,

HH, andA/A,A/O or A/B

genotypes.

The B antigen is found on

the RBCs when there isHh,

HH, andB/B,B/O or A/B

genotypes.


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Amount of H Antigen According to Blood Group

Blood Group O peoplehave red blood cellsrich in H antigen.

Why?

Neither the A or B genes have converted the Hantigens to A or B antigens - just a whole bunch ofH!

O allele at the ABO locus (amorph)It does not alter the structure of Hsubstance.

GreatestAmount of H

LeastAmount of H

O > A2 > B > A2B > A1 > A1B


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Donor Nucleotides & Immundominant Sugars responsible

for H, A, and B Ags specificity

AntigenImmunodominant sugarNucleotideGlcosyltransferaseGene

HL-fucoseGuanosine

GDP-FUC

L- fucosyl trnsferasH

AN-acetyl-D-galactoseamine

Uridine

UDP-GALNAC

N acetylgalactosaminyl

transferaseA

BD-galactoseUridine

UDP-GALD- galactosyltransferase

B

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ABO blood system

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