ABO blood group system has many antigens. We will discuss about their roles and functions.

1. Prepared by: Anish Dhakal
anishdhakal718@gmail.com

2. Objectives
• Brief History of ABO Blood Group
• Antigenic determinants of blood groups
• ABO Blood group System
• Incompatibility and Complications due
to Mismatched Blood Groups
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3. History of ABO System
• Karl Landsteiner at the
University of Vienna
• Discovered reason behind
why some transfusions are
successful while others were
deadly
Discovered in 1900
Nobel Prize in 1930 3

4. History of ABO System
• Landsteiner identified three types A, B
and C
• C was later to be re-named O for the
German “Ohne”, meaning “without”, or
“Zero”, “null” in English
• The fourth less frequent blood group AB,
was discovered a year later 4

5. ABO Blood Group
• Classical example of multiple allelism in
chromosome no. 9 (9q34.1)
• A and B alleles are codominant
• O allele inherited as recessive trait
• Special feature: Antigens on RBC have
reciprocal relationship with antibodies in
Plasma 5

6. What are ABO Blood Group
Antigens???
• Cell surface Glycosphingolipids
• Individuals inherit the gene to code
which code for specific sugar added to
the RBCs
• Controlled by ABH genes
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7. RBC Precursor Structure
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8. Formation of H Antigen
(Role of L-Fucosyl Transferase)
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9. Formation of A Antigen
(Role of N-acetylgalactosaminyl
Transferase)
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10. Formation of B Antigen
(Role of Galactosyl Transferase)
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12. Inheritence of ABH Antigens
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13. Bombay Phenotype
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14. Bombay Phenotype
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15. Landsteiner’s Law
• If an antigen is present on the surface of red
cell membrane, its corresponding antibody must
be absent in the plasma and if an antigen is
absent in the red cell membrane, its
corresponding antibody must be present in the
plasma.
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17. Origin of Agglutinins in
Plasma in absence of RBC
Antigen???
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18. Titer of Plasma Antibody
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19. Clinical Manifestations of
ABO Incompatibility
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20. Fetal Immune Hydrops
• Accumulation of edema fluid in fetus
• Blood Group and Rh incompatibility
• ABO incompatibility in 20-25% of pregnancy
• Laboratory Hemolytic Evidence: 1 in 10
• Severe Hemolysis: 1 in 200
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21. Fetal Hydrops:
ABO Vs Rh Incompatibility
• Less common and severe hemolysis in ABO
incompatibility because:
 Most Anti-A and Anti-B antibodies are IgM type so
don’t cross placenta
 Neonates cell express Antigen A and B poorly
 Expression of Antigens A and B by many cells
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22. Measures to Ensure
Compatibility
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