Blood group types Classification #hematology #blood_bank

1. Blood group systems
• Approximately there were 400 red cell group
Antigens have been described
• The most clinically important are ABO, Rh
• Other blood group e.g
• Duffy, kidd, kell, Lewis,MNS blood group
systems .

2. ABO blood group system
• The ABO is the most important blood group system in
blood transfusion
• History of ABO blood group system
• Landsteiner discovered the ABO blood group system in
1901
• He and five workers began mixing each other red cell and
serum together and accidently performed the first forward
and reverse ABO grouping .
• Landsteiner rule
• If an antigen is present on patient red blood cells the
corresponding antibody will not be present in the patient
plasma in normal conditions

3. Classification of ABO groups
• There are 4 group of ABO system named
according to the Ag present on the red blood
cell surface
Blood group Ag present Antibody present
A A Anti B
B B Anti A
O None Anti A & Anti B
AB A and B None

4. Inheritance of the ABO
• There are three allelic genes (A,B and O )each
individual inherits two , one from each parent
• These genes determine which ABO antigens
will be present on the red cell , A and B
antigens is dominant antigen .
• A antigen could be divided into subgroups A1
and A2
• Allele is a variant form of gene ,which are
located at same position on a chromosome.

5. Phenotype and genotype
Phenotypes Genotypes
A1 A1A1 - A1A2 - A O -
A2 A2A2 - A2O
B BB - BO
A1B A1B
A2B A2B
O OO

6. Biochemistry of A, B, H Antigens
• ABO antigens are located on RBCs, lymphs, platelets,
tissue cells, bone marrow and solid organs.
• Not fully developed at birth, fewer copies of the
antigen on the cells
• Antigens ARE NOT direct products of the genes.
• Genes code for TRANSFERASE which causes transfer
of monosaccharide molecule onto a precursor
substance on the RBC.

7. H Gene
• H gene Codes for the production of fucosyl transferase that catalyzes the
addition of L-fucose, and form H antigen.
• H substance or H antigen is the complex of precursor substance and L-
fucose sugar( terminal carbohydrate backbone ) on which A and B antigen
are synthesized .
• The H gene and its allele h are inherited independently of the allelic A, B
and O genes
• If only H antigen is present, the individual is group O.
• Once L-fucose added, A and B gene specified products can add their
sugars.

8. The role of H gene in the expression of
A and B genes
• The expression of A and B genes found to be
depended on the action of another gene
known as H gene .
• Most individuals are homozygous for that
gene ( HH ).
• Genotype (hh)is extremely rare the Bombay
phenotype

9. A Gene
• Codes for production of a galactosaminyl
transferase.
• It adds N-acetyl-galactosamine to the preformed
H-substance .

10. B Gene
• Codes for production of a galactosyl transferase
• It adds D-galactose to the same H substance .

11. The genetic sequence leading to
expression of ABH gene on red cell
• The precursor substance of all antigen is converted by the H gene to
H substance by addition of L- fucose .
• This H substance is partially converted by the action of A and B
genes into A and B antigens by addition of certain sugars .
• Some of the H substance remain unconverted
• Genes code for TRANSFERASE which causes transfer of
monosaccharide molecule onto a precursor substance on the RBC
• the O gene is amorphic effect no conversion on the H substance
so H substance found in greatest concentration in group O.
•

12. A, B and H
• If only the H antigen is present, the person is group O
• If the A antigen (N-acetyl-galactosamine) is present,
the person is group A
• If the B antigen (D-galactose) is present, the person is
group B
• If both structures of the A & B antigens are present, the
person is group AB

13. • In the absence of H gene , no H substance will
be obtain and A and B genes in this case will
not be expresses.

14. Oh the Bombay phenotype
• Found in individual who lack the H gene they
are hh genotype
• Since the H gene required for the conversion
of the precursor substance into H substance
• Individual of genotype hh can not produce A
or B antigens so they appear to be O Bombay
they have no A , B or H substance in their red
blood cell.

15. The ABO antibodies
• Anti A and anti B
• Are produced by individual who lack A and B respectively.
• They are IgM type
• They can react at body temperature and activating complement
causing red cell destruction .
• Anti A1
• Are naturally occurring IgM antibody produced by A2 and A2B
individuals it is of no clinically significant .
•
• Anti H
• It occur as IgG or IgM in the serum of Bombay group.
• It is high thermal range and able to activate the complement it is
clinically significant .

16. The secretor gene
• The A, B and H antigens are found in plasma ,
saliva and other body fluids their presense in
these fluids is controlled by autosomal
dominant secretor gene (Se)
eg:
• Group A secretor has A , H substance in his
body fluids
• Non secretor (sese)do not have ABH blood
group antigens in their body fluids .

17. • thanx