Blood Groups Flashcards
When did the 1st successful blood transfusion happen? Who did it?
1818, by James Blundell
Who discovered blood groups?
Karl Landsteiner
In 1901 Karl Landsteiner discovered ABO blood groups through
Agglutination patterns: he noticed agglutination of blood when mixed with others
which blood groups did Karl Landsteiner discover?
A, B, C (O) blood groups identification
Group A blood has antibodies to…
Group B (anti B)
Group B blood has antibodies to…
Group A (anti A)
Group AB blood has antibodies to…
None
Group O blood has antibodies to…
Both A and B (anti A & B)
Which group’s plasma would be the best to give to any individual (fool-proof)?
Group AB, as it has no antibodies
Whose red blood cells would be the best to give to any individual (foolproof)?
Group O (no antigens)
Are there only ABO blood groups
No, there are many! Approx 400 blood groups
What is the basis of transfusion reactions?
Individuals who lack an antigen may produce antibodies if exposed to that antigen. Ab may cross the placenta and cause haemolytic disease in the newborn.
Where are ABO blood groups located and how are they inherited?
Presence of A, and B antigens on the red cell surface
A and B antigens present on RBC at birth
Mendelian inheritance
In the plasma/serum, there are anti A and B antibodies present, when…
Present if lack A and B antigens respectively
Naturally occurring
Appear after 3 months of birth
Biochemistry of ABO blood groups
There is only a minor difference between A and B antigens
Although immunologically quite distinct
They have the same backbone sugar molecule (H antigen), only the terminal sugar is different
A and B produced from the H gene
H gene encodes an enzyme that adds fucose (sugar) to the terminal sugar of a precursor substance (H antigen)
Blood groups A and B are “built on” H antigen
A and B genes encode enzymes that add a sugar to H
“A” gene codes for an enzyme (transferase) that adds N‐acetylgalactosamine to the terminal sugar of the H antigen
The “B” gene codes for an enzyme that adds D-galactose to the terminal sugar of the H antigen
3 allelic genes: A, B, O
A and B genes control synthesis of different enzymes
O is “null” – i.e. no enzyme produced from that allele
The enzymes are responsible for addition of specific carbohydrate residues onto a membrane glycoprotein (substance H)
How are the ABO blood groups inherited?
Autosomal dominant, mendalian inheritance of the ABO blood groups
Child blood group determined by parents
What type of antibodies are anti-A and anti-B?
IgM antibodies
Naturally occurring: produced at 3-6 months
They rarely cross the placenta as they are big molecules (pentameric antibody)
What can anti-A and B antibodies cause?
Anti-A and B antibodies can cause clinically significant problems:
Cause rapid intravascular haemolysis (within blood vessel)
Severe immediate transfusion reactions (intravascular)
Cause mild haemolytic disease of the newborn (Group O mother; Group A baby)
What is the most frequent blood group? then?
O - 46%
O > A > B > AB
What are the blood group frequencies for the rest of the blood groups:
A - 39%
B - 11%
AB - 4%
How many antigens are present in the Rhesus Blood Group system?
40
How does the rhesus blood group system work?
D gene is either present (RhD positive) or absent (RhD negative)
The presence or absence of D determines Rh positive or negative
why is RhD important
Rhesus D is important
The RhD antigen is highly immunogenic (able provoke immune response)
Important in haemolytic disease of the newborn
How many Australians are Rh(D) positive?
85% the D gene is present
