PSC1002/L04 Blood Groups Flashcards
Describe the work of Karl Landsteiner (1901). (3)
The ABO blood group system
Identified 3 blood types A, B, C
AB discovered 1 year later
Define a blood group.
Classification of blood based on presence (or absence) of inherited antigenic substances on surface of RBCs
Describe antigens of RBCs. (2)
Complex mixture of proteins, glycoproteins and glycolipids
Found on surface of all RBCs and range of other cells in body
How many human blood groups systems/antigens are known?
43
>600 blood group antigens
What is the +/- of a blood group?
Presence or absence of Rhesus D antigen
What 5 sugars make up RBC antigens?
Fucose
Galactose
N-acetylgalactosamine
N-acetylglucosamine
Sialic acid
Which enzymes are involved in blood groups? (3)
Fucosyl transferase (FUT1)
N-acetylgalactosamine transferase (A transferase)
Galactose transferase (B transferase)
Which 2 genes are involved in blood group?
ABO
H
What kind of enzyme do ABO and H genes encode?
Glycotransferases
Name the alleles found at the ABO and H loci.
A, B, O
H or h
What protein does the O (recessive) allele encode?
Truncated, non-functional protein
What enzyme does the dominant H allele encode?
Fucosyl transferase
Where is the H gene located?
Chromosome 19
What is the ‘Bombay’ phenotype?
hh genotype
No symptoms or related disease
Can only receive transfusions from the same blood group
Where is the ABO gene located? How many exons does it have?
Chromosome 9
7 exons
What is the difference between the A, B and O alleles?
A&B differ by 7 nucleotide substitution - 4 different aa
Residues at 266&268 determine AB specificity
O: deletion in exon 6 - frameshift
What is needed to catalyse the reaction of A&B transferase?
UDP
What disease susceptibility is linked to ABO phenotype? (2)
Gastric cancer in group A
Gastric and duodenal ulcers in group O
What effect does blood group have on factor VIII and vWF?
Group O have 25% less factor VIII and vWF in plasma
What are blood group antigens/corresponding antibodies known as?
Agglutinogens
Agglutinins
Describe haemolytic transfusion reaction. (3)
Donated RBC lyse in blood vessels
Complement system is activated
Leads to kidney failure, uncontrolled clotting , circulatory shock
Describe how anti-Rh(D) antibodies destroy Rh(D)+ RBCs. (3)
RBC bound by IgG
Engulfed by macrophages
Transported to liver and spleen for removal
What is the universal donor and recipient blood type?
Donor: O-
Acceptor: AB+
What must be considered when finding a blood match? (2)
Donors antigens
Recipient’s antibodies
When can new born haemolytic disease occur? (3)
Rh+ father and Rh- mother
Rh+ blood from foetus enters mother’s blood during delivery; mother produces anti-Rh antibodies
If pregnant again with Rh+, antibodies damage foetal RBC
What class of antibodies are mother ABO antigens?
IgM
