Chp 4 ABO groups and Hh blood group systems
ABH antigens in secretions are
Primarily glycoproteins
Antibody to A1 subgroup
Produced by 1-2 % of A2 and 20-25% of A2B people Is naturally occuring IgM Clinically insignificant unless reactive at 98.6 degrees celcius
Ways to identify A subgroups
Strength of reaction with anti-A, anti-B and anti-A,B Reaction or non reaction with specific anti-A clones Strength of reaction with anti-H lectin (ulex europeus) Presence or absence of A and H in the saliva of secretors
What percentage of people are secretors and what are the possible genotypes
80% SeSe or Sese
A antigen is made by the product of the
A gene: 1, 2 N-acetyl-galactosaminyltransferase which adds teh immunodominant sugar N-acetyl-D-galactosamine to the H antigen.
Anti-IH antibody
A weak cold reactive anti-body that is not clinically significant. Produced by para Bombay people as well as group A1 people (they have the least amount of H substance in their blood)
Group A subgroups
A1, A2 80% of Aand AB people have A1 gene. 20% have A2 gene. A1 gene is more efficient at converting H substance to A antigen therefore A1 cells have more A antigen on RBCs than A2 B cells
Freqency of A subgroups
A1>A2>A3>Ax>Am>Ael
Which Blood group has the least amount of H substance A1B, A2, B, O
A1B
Which subgroup of A is known for displaying mixed field agglutination with human anti-A
A3
Which subgroup of A is noted for displaying mixed field agglutination with human anti-A
A3
Anti bodies present in Bombay phenotype people
Anti-A, anti-B, antiA,B, anti-H
Naturally occurring antibodies
Antibodies which occur without any apparent stimulus
B gene product is
B:gene: 1,3-D-galactosyl transferase which adds the immunodominant sugar D-galactose to the H antigen
Type 2 chains found in
Blood cells
What is the difference between Bombay and para Bombay phenotype
Bombay phenotypes lack the H antigen in both their blood cells and secretions hhhh sese para Bombay lack the H antigen on blood cells but have it in secretions hhhh Sese or hhhh SeSe
Cis AB
Both AB genes are on one chromosome and O gene is on another. Maybe due to a gene mutation or a cross over event. people may be indistinguishable from AB, or sometimes they produce an ABO discrepancy due to weak expression of A or B antigen.
Detecting Bombay phenotype
By using autocontrol (testing a patient cell with patient plasma) and anti H-Lectin
H and Se genes
Chromosome 19 close to each other. se and h are amorphs
Intravascular hemolysis
Destruction of blood cells in the veins and arteries.
type I chains are found
In secretions (urine, plasma, saliva, milk) and gut lining.
What type of mismatch is present if group O donor hematopoietic progenitor cells are transplanted to a group A recipient.
Minor
What are the two chains which are precusors to the ABO blood group antigens and the 3 genes which act on them
Type 1 chain Type 2 chain H gene (chromosome 19) Se gene (chromosome 19) ABO gene (chromosome 9)
How can the secretor status of a person be determined?
Presence of Lewis antigens, because Le and Se loci together determine the lewis phenotype. Test is saliva inhibition test.
Difference between type 1 and type 2 chains
Type 1: Last galactose bound to subterminal glucosamine by a beta 1-3 linkage Type 2 :last galactose bound to subterminal glucosamine by a beta 1-4 linkage
What biochemical structure most commonly carries the ABO and Hh antigens on the red blood cell membrane.
glycoprotein
Para Bombay phenotype and genotype
. They are hh and have at least one Se gene. They have H, A or B antigens in their secretions and plasma. Sometimes some A and B antigens will adsorb onto the RBC membrane from their plasma and lead to a weak expression.
Se gene product
FUT2 . 1,2 L- fucosyl transferase (similar to enzyme coded by H gene) Adds a fucose to the terminal galactose to type 1 chains. It makes the H antigen in secretions
What are the two components of blood group testing and how is each performed
Forward and reverse groupings. Forward group tests unknown RBCs with known commercial anti-A and anti-B reagents. The reverse group tests unknown plasma with known commercial A1 and B cells.
ABO antigens are
Glycoproteins
H antigens on blood cells are made by the product of the
H gene: !, 2, L fucosyl transferase (FUT1) which acts on Type 2 chains and adds an L- fucose to the termial galactose of the H antigen precursor
Bombay phenotype
No H substance on their blood cells or secretions. Genotype is hehe, sese. Blood cells also lack A,and B antigens regardless of ABO genotype because H substance cannot be converted to A and/or B antigen
What type of RBCs should be transfused to a patient with an unresolved ABO discrepancy? What type of plasma should be transfused to the same patient if needed
O blood and AB plasma.
Which gene in the ABO blood group is an amorph
O gene
Amount of H antigen
O>A2>B>A2B>A1>A1B
ABO antigen frequency
O>A>B>AB
H group antigen precursor
The precursor of the H antigen lacks the fucose sugar
When is saline replacement preformed
When rouleaux is suspected
sese
non secretors 20% of population. 80% are secretors
Lack of ABO antigens in secretions is due to
sese
