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