2 ABO Blood Group System

• ABO Blood group system is the most important of all human blood groups. It was the first blood group system to be discovered by Dr. Karl Landsteiner in 1900s; unique among 36 blood group system
• ABO group is the only blood group system with predictable antibodies in the serum to antigens not present on RBCs
• The basis of determining the phenotype is through the presence of A and B on the surface of RBC.
• Development of anti-A and anti-B without RBC could be due to exposure to A- and B-like antigens from a bacteria
• Transfusion of incompatible ABO type results to almost immediate lysis of donor RBCs, which may be severe to fatal
• Incompatible blood type can activate complement proteins that produces the terminal effect of hemolysis.
• Type O

  
• Type A

  
• Type B

  
• Type AB

  
• There is a reciprocal relationship between the antigen and antibodies of ABO blood types
• Frequency of type O blood group in the Philippines

  
• Frequency of type A blood group in the Philippines

  
• Frequency of type B blood group in the Philippines

  
• Frequency of type AB blood group in the Philippines

  
• Inheritance in ABO blood group is described by Bernstein in 1924, where one (1) gene from each parent determines the genotype of the offspring.

  • Inherent 1 haplotype from one parent
  • 1 haplotype from another parent

  = when combined, you will have the genotype
• The ABO blood group inheritance follows the mendelian genetics, which is co-dominantly expressed.
• All ABO genes are expressed co-dominantly, which means that both genes will be expressed equally
• Chromosome 9 is where the ABO gene can be found
• The O gene is an amorph gene, which does not produce any observable characteristics; silent gene
• H antigen is the precursor of A and B antigen. Without it, A and B cannot be formed.
• Our A and B as well as H gene are also seen in bodily secretion such as plasma, urine and saliva
• Formation is a result of interaction between the following genes:

  • ABO and H genes → H, A and B antigen on RBC membrane
  • ABO and Se genes → H, A and B antigens on secretions
• Each gene codes for a glycosyltransferase, where enzyme transfers an immunodominant sugar to a basic precursor substance composed of:

  • glucose
  • galactose
  • n-acetyl-d-glucosamine
  • another galactose
• Immunodominant sugar are carbohydrates or sugar that confer antigenic specificity. In other words, it is the antigenic determinants of epitopes
• Precursor substance

  • Type 1 → in secretions
  • Type 2 → on RBC membrane
• Immunodominant sugar - type 1

  
• Immunodominant sugar - type 2

  
• Immunodominant sugar is a sugar that occupies the terminal portion of the precursor chain and converse blood group specificity; it provides antigenic specificity
• Immunodominant sugars:

  • H-antigen → L-fucose is added to the precursor substance
  • A-antigen → H antigen + N-acetyl-D-glucosamine in other side of terminal galactose
  • B-antigen → H antigen + D-galactose
• The expression of H and Secretor genes follow the dominant and recessive types
• Bombay Phenotype is when one have the double dose of the recessive H antigen, which precursor structure is unchanged
• Type O has the greatest amount of H antigen, while Type A1B has the least amount.
• ABO antibodies are predominantly IgM, which produces strong agglutination at <RT and activates C’ at 37°C

  • has small quantities of IgG
  • it becomes detectable at 3-6 months of age
  • causes rapid intravascular hemolysis and can cause death
• IgM participates in agglutination reaction, it is cold-reacting and pentameric.
• In type O, IgG has a higher titer
• Knowledge on the amount of IgG ABO antibiotics allows prediction of ABO HDFN (Hemolytic disease of the fetus and Newborns)
• Forward Grouping lab test is the detection of A and/or B antigens on the surface of RBCs

  Reagents: Antisera – monoclonal antibodies

  • Anti-A antisera (blue) → binds to N-acetyl-d-glucosamine; uses Trypan Blue Dye
  • Anti-B antisera (yellow) → binds to terminal galactose; uses Acriflavine yellow dye
  • Anti-H → true type O or Bombay phenotype blood type O
• Reverse Grouping lab test is the detection of A and/or B antibodies on the surface of RBCs

  Reagents:

  • Known A/A1 cells
  • Known B cells
  • Known O → used to check if Bombay phenotype
• Lectine Sources are plant extracts that demonstrate antigenic specificity similar to antisera

  • Anti-A → Dolichos biflorus
  • Anti-B → Griffonia simplicifolia
  • Anti-H → Ulex europaeus