The ABO Blood Group System Flashcards
Who discovered the ABO Blood group system
Karl Landsteiner
When was the ABO blood group discovered
1901
What were the original three blood groups
A B and C
When was the AB blood group found?
1902
Where is the ABO locus found?
Chromosome 9
What type of antibody are the ABO antibodies?
IgM
When was the A group subgroup found?
1930
Why are ABO antibodies clinically significant
These are potent activators of complement
Why are ABO antibodies not found in babies
Babies don’t have antibodies yet
How do anti ABO antibodies come about?
(3)
You don’t have a gut microbiome yet
When gut flora develops, these have antigens which are similar to those found on rbcs
You develop antibodies to the antigen you don’t have
What is significant about the group O antibodies
These antibodies (anti-A and anti-B) are IgG
What is considered a major reaction in a transfusion
Wrong red cells
If you give A type blood to an O type person the individual kept producing anti A antibodies
What is considered a minor reaction in a transfusion
(3)
Wrong plasma
If you give anti A plasma to an A red blood cell type
Anti A plasma will attack the person’s A rbcs but this will eventually run out
What is Landsteiner’s rule?
This states that healthy individuals possess ABO antibodies to the ABO blood group antigens absent from their RBCs
When were the ABO groups first put to practice?
(3)
1917
Transfused battlefield casualties in France
All were group O donations (universal donors)
How would you describe the genetics of the ABO blood group system?
Blood group antigens are codominant
What three genes influence the occurrence and location of ABO antigens?
ABO
H
Se
What does the H gene control?
The presence or absence of the ABH antigens on the rbc membrane
If you have H you have antigens
If you dont have H you dont have rbc antigens
What does the Se gene control?
(3)
The presence or absence of the ABH antigens in secretions
If you have Se then you will have ABH antigens in secretions
If you dont have Se then you will not have ABH antigens in secretions
What are the two H gene alleles
H and h
What is someone with the hh phenotype called?
The Bombay phenotype
Where is the H gene located
Chromosome 19
What is the h allele?
Its a damaged H allele -> very rare
Two hs will result in no antigens being expressed
How does the H gene actually work?
It adds a L-Fucose
This acts as the substrate for ABO antigen
Many people have an anti-H antibody, describe this
It’s a cold antibody
It’s usually benign in the body at 37 degrees but when outside the body and it cools they can cause problems
What acts as the basic precursor structure for the rbc antigens?
An oligosaccharide chain
What is the oligosaccharide chain attached to?
Attached to a protein or lipid carrier molecule
What does the H locus encode
An alpha 1,2 fucosyltransferase (FUT 1)
What does the A locus encode
alpha 1,3 N-acetylgalactoaminyl transferase
What does the A locus encode
alpha 1,3 N-acetylgalactoaminyl transferase
What does the B locus encode
alpha 1,3 galactosyltransferase
What does the Se gene encode?
An alpha 1,2 fucosyltransferase (FUT 2)
By how much do the A and B genes differ from each other
They differ by 7 single base substitutions
How does the O gene differ from the A gene
Differs by a single base deletion
This results in the translation of a protein that does not produce an antigen
What are the two A subtypes
A1 and A2
How does A1 differ from A2
A1 enzyme is 5 to 10 times more active than the A2 enzyme
What percentage of As are A1?
80% are A1 and 20% are A2
Comment on the antibodies in A2 blood type
Some people have both anti-B and anti-A in their plasma
What percentage of people are secreters of rbc antigens
Approximately 75%
Write a note on the Bombay phenotype
(5)
hh phenotype
Only 2 families in Ireland have this
You dont have any ABO or H on your rbcs
Anti-A, Anti-B and anti-H
Only autologous units or rare donor files can be used -> families can donate blood and it will be frozen
What percentage of the Irish population is group O
55%+
What percentage of the Irish population is group A
Approx 30
What percentage of the Irish population is group B
Approx 10
What percentage of the Irish population is group AB
Less than 5%
What is considered the universal donor
Group O
What is considered the universal recipient
Group AB
What is considered the universal recipient
Group AB
What is octaplas
A blood plasma product
What specific type of O blood is given to women
O-
What specific type of O blood is given to men
O+
What types of plasma can be given to group O patients
B plasma -> Anti A plasma
A plasma -> Anti B plasma
O plasma (anti A and anti B plasma)
Uniplas
What type of plasma can be given to group B patients
Uniplas
B group (anti-A plasma)
What type of plasma can be given to group A patients
Uniplas
A group (anti-B plasma)
What plasma can be given to AB group
Uniplas
Who can group O octaplas be given to?
Group O patients
Group O can get platelets from who?
O
A
B
AB
Group B can get platelets from who?
B, A or AB
Group A can get platelets from who?
A, B or AB
Group AB can get platelets from who?
A or B
Why do you rarely give group O platelets?
Anti A and B antibodies
How does a mismatch occur?
(2)
Wrong unit is administered
Wrong sample is in the tube (wrong person’s blood)
What happens in a mismatch
Intravascular haemolysis
Classical complement pathway activation
Renal Failure
