ABO system Flashcards
What is the most common blood group in Ireland
O+
What is the least common blood group in ireland
AB-
Who was the ABO blood group system first described by and when?
Karl Landsteiner in 1901
Why is the ABO system the most clinically important blood group system in transfusion
- Nature of the ABO antibodies -> they are mainly IgM and cause intravascular haemolysis of incompatible red cells via complement activation.
- ABO incompatibility accounts for a significant number of fatal haemolytic transfusion reactions.
Reasons for severe haemolytic transfusion rxns (4)
- Mislabelling of blood sample -> patient sample A being labelled with patient B details for blood grouping
- Mislabelling donated blood packs -> blood packs are labelled with the name and other identifiers of patient receiving the blood
- Transfusing the wrong patient
- Serological errors -> patient or donor blood misgrouped in the lab
Where are the three common alleles (A, B and O) located
At the ABO locus on chromosome 9
What is located on chromosome 19
The H and h alleles
What are the foundation blocks for the building of the ABO blood group antigens
Oligosaccharide chains
Where are these oligosaccharide chains found
Red blood cells have the oligosaccharide chains attached to the membrane
What does the H gene code for
The transferase enzyme that adds fucose to the precursor oligosaccharide chains on the red cell membranes
What does the H antigen act as
The precursor material on which A and B antigens are built
What do the A and B genes encode
A transferase enzyme
What does the transferase enzyme encoded by the A and B genes do
It acts upon the H precursor antigen material to produce the A and B antigen
What is the O gene known as and why
It is known as an amorph (is silent). This is beacuse the O gene does not encode a functional enzyme and therefore does not produce a detectable antigen
What do the red cells of a group O person have
An abundant amount of H antigen but no A or B antigens