Blood Group Antigens and ISBT

• Blood group antigens are components of the red cell membrane.
• Their expression relies on the inheritance of specific blood group genes.
• They are categorized as either carbohydrates linked to lipids (glycolipids) or proteins (glycoproteins).
• Exposure to these antigens via blood transfusion or pregnancy may lead to the production of antibodies against the lacking antigen in the recipient.
• Red blood cells carry distinct sets of antigens unique to each individual.
• A specific antigen can trigger the formation of a specific antibody, leading to the destruction of cells containing the antigen.

ISBT (International Society of Blood Transfusion)

• There are 36 registered blood group systems recognized to date.
• ISBT was responsible for organizing the gene names and numbers.
• They are responsible for standardizing the terminology for red cell antigens to provide terminology suitable for computer software use.
• This was done by creating a working committee on the terminology for red cell antigens in 1980.
• Did not replace terminology, but provided additional terminology.

Red Blood Cell Composition

• Red cells are mainly composed of proteins, both external and internal.

Blood Group Antigen Dependence

• The presence of blood group antigens hinges on the inherited gene, leading to variations in red cell membrane proteins regarding forms, sizes, and length.
• Blood group antigens exhibit varying expression on the red cell membrane, based on the type of red blood cell protein involved.

Hh Blood Group System

• Included in the ABO blood group system due to their special interconnection.
• ABO blood group antigens cannot exist without the presence of the H gene.

Karl Landsteiner

• Karl Landsteiner discovered ABO blood groups in 1901.
• He paved the way for the study of immunohematology and blood transfusion medicine.
• Karl Landsteiner was the first person to perform ABO forward and reverse blood grouping.
• He drew blood from himself and his associates, separated the cells and serum, and mixed each cell sample with each serum.
• He recognized different patterns of agglutination when human blood samples were mixed in random pairings.
• He assigned blood groups as A, B, and O.

Landsteiner's Law

• Normal and healthy individuals possess ABO antibodies to the ABO antigen absent from their red cells.
• An individual with a specific ABO antigen will possess an antibody against any antigen not present on their red cells.
• A person cannot produce an antibody against their own antigen.

ABO Blood Type Example

• Type A individuals lack the B antigen; therefore, their plasma contains anti-B antibodies.
• Type B individuals lack the A antigen; therefore, their plasma contains anti-A antibodies.

Blood Typing

• Determines the blood group of an individual.

Forward Typing

• Identifies antigens present on the red cell surface.
• Utilizes antisera as a reagent, containing antibodies specific to antigens potentially present on the red cell.
• Requires a red blood cell sample.

Reverse Typing

• Determines antibodies present on the patient's plasma.
• Uses plasma or serum samples.

Making Use of Known Red Cells

• Identifies red cells that contain A antigens and those with B antigens to check reverse typing.
• The antibody of the patient will react with the A antigen, therefore it has Anti-A = Blood type b.

Data from the National Voluntary Blood Services Program (NVBSP)

• The most common blood type is blood group O, followed by A, then B, and lastly AB.
• The distribution of blood types in the US population is the same as as the frequency of Filipino blood types.
• Most Filipinos are Rh positive, while only 1% are Rh negative.
• Blood Group O individuals are universal donors meaning that Group O packed red cells can be transfused to A and AB individuals.

Inheritance of A, B, and O Antigens

• According to Bernstein (1924) and the multiple allele theory:
• The inheritance of A, B, and O antigens means that an individual inherits one ABO gene from each parent.
• These two genes will determine which ABO antigens are present on the red cell membrane.
• The expression of the A, B, and O antigens hinges on inherited genes from your parents.
• These genes are located on one locus in chromosome 9.
• Interaction of (3) genes at 3 separate loci (Basis for expression or formation of ABO antigens.)
  • ABO
  • Hh
  • Se

Codominance

• ABO cannot be expressed in the red cell if there is no Hh antigen/gene.
• ABO could not be expressed in the secretion if there is a lack of secretor (Se) gene.

Mendel's Genetics

• If one parent gives you the A gene and one parent contains the O gene, you are going to have the phenotype A.
• A is dominant over O because O is the recessive gene.
• The phenotype of an individual depends on the genotype of the parent:
  • If homozygous: the double dose of the gene
  • If heterozygous: two different genes
• Could either be that both genes are dominant or one is dominant and the other one is recessive. Genotype: The gene that was taken from the parent
  • If you have A and O = Heterozygous
    • Genotype = AO
    • Genotype = AO will appear in the red cells
• The dominant gene can be your basis for your phenotype.

The Precursor Substance

• The inheritance of the ABO gene does not directly produce an antigen.
• Instead, it produces a specific enzyme, termed Glycosyltransferases.
• Paragloboside
  • An oligosaccharide chain attached to a protein or liquid molecule.
  • Is a basic precursor substance of the A, B, and H antigens.
  • Mainly composed of oligosaccharide chains.

Oligosaccharide Chains

• Changed by:
  • Adding specific sugar by the enzyme (glycosyltransferases)
    • Produced by a type 1 or 2 substance.
• Glucosyltransferases
  • [Glycosyl =sugar | Transferases = transfer]
  • Is an enzyme produced by the gene
  • Transfer sugar molecules on a precursor substance in order to make it a specific ABO antigen and that precursor substance is known as PARAGLOBOSIDE.

Type 1 Precursor Substance

• Found in:
  • secretions (plasma, saliva)
    • body fluids
• Three molecules of paragloboside
  • Galactose(2)
    • Contains the terminal sugar
    • Beta-1,3-linkage
    • 1st carbon attaches to the 3rd carbon of N-acetylglucosamine
  • N-acetylglucosamine
    • (GlcNAc) is attached to the previous sugar molecule
    • (Galactose) via Beta -1,3 linkage.
  • Found in the body fluids and secretions.
    • Mainly because the terminal galactose is attached to the preceding sugar with the N-acetylglucosamine via the Beta 1-3 linkage.
• *Remember**sugar molecules have 2 forms, could be an alpha or beta depending on the position of the OH on the first carbon or anomeric carbon
  • Beta = OH is above the ring while the H is below the ring
  • Alpha = OH is Below the ring while the H is above the ring

Type 2 Precursor Substance

• Found in: - The red cell membrane
• Made of the three molecules of paragloboside
  • Galactose (2)
    • With regards to the terminal is Alpha 1,3
  • N-acetylglucosamine
    • Beta 1,4 linkage -Type 2 is same with type 1- differs based on the 1,4 attachment via Beta glucose

Formation of H antigen

Recaps

• The only antigen found in the H blood group system.
• The formation of H antigen is mainly through the inheritance of the H gene.
  • H gene is closely linked to Se gene, in which they are in the same loci found in Chromosome 19 -The alleles of H gene is H and h -"h" - the recessive allele -"H" - dominant allele double dose of the h allele (hh) = no expression of the H antigen on the red cell.
• The inheritance of the H gene will not directly form the H antigen, rather it will code for a specific enzyme known as Alpha-2-L-fucosyltransferase.

Amorph

• If you have inherited a double dose of the amorph allele of h gene(hh)= no secretion of the Alpha-2-L-fucosyltransferase
  • no addition of fucose to the terminal galactose of the paragloboside
  • All paraglobosides will remain as is and conversion to H antigen will not occur.
• Bombay phenotype (hh)
  • silent h allele
  • The first individual found to have such phenotype was found in Bombay, India.

Gene Product

• Alph-2-l-fucosyltransferase will transfer the fucose to the 2nd carbon of the terminal galactose.
• Forming the H antigen, and the fucose is the immunodominant sugar.
• Because the A gene is also inhertied, then Alpha-3-N-acetylgalactosaminyltransferase is coded, forming the immunodominant sugar of a gene.

Formation of A antigen

• The A antigen expression is dependent on the inheritance of the ABO gene.
  • AA (homozygous) or AO (heterozygous) If you have double double A (AA)or a heterozygous version which includes both (ABO):
  • able to express A antigens on their red cell. Alleles: A, B, and O Found on Chromosome 9 In order to express the A antigen, the individual must have the A gene. But it could also occur with the combination of A and the amorph ABO gene(O). The inheritance of the A gene will not directly from the A antigen. Rather, it will produce a specific enzyme in the form of Alpha-3-N-acetylgalactosaminyltransferase. Alpha-3-N-acetylgalactosaminyltransferase will transfer the sugar, N-acetyl-D-galactosamine. The paragloboside must be converted first to H antigen before it is coverted to A antgen. Inheritance of A or B antigen while lacking the H gene will prevent the paraglobosides from being converted to H antigen. Therefore also preventing the formation of A and B antigen.

Formation of B antigen

• Expression of B antigen is dependent on the inheritance of ABO gene, particularly B allele.
  • BB (homozygous) or BO (Heterozygous) The first individual found to have such
• has the B antigen. But because the B gene is also inherited, then
• Alpha-2-L-fucosyltransferase is coded, which will transfer the D-galactose via 1,3 attachment via 1 3 attachment to the terminal galactose of the H antigen

Secretor Genes

• Non-secretor
• Can also be RBC • •

Note

• The inheritance of ABO gene
• But 00