Flashcards in Blood groups Deck (16):
True or False: The ABO system is a protein based system.
False: it is a carbohydrate based system.
What system does Rh belong to?
It is a protein based system.
How many alleles are involved in the ABO system and what are the names?
There are three alleles; IA, IB and IO. It stands for Isoagglutinin.
What enzyme does the A allele code for?
What enzyme does the B allele code for?
How can you differ between the type of precursor chains?
It depends where the Galactose binds to the sub-terminal N-acetylglucosamine(GlcNAc).
Explain the details of Type 1 chains?
They are primarily glycoproteins, they are found in secretions, it is a Beta1-3 linkage.
Explain the details of Type 2 chains?
They are primarily glycolipids, found on cell surface, Beta1-4 linkage.
FUT2 gene codes for a1,2-fucosyl transferase 2, what type of chain does this enzyme add fucose to?
It adds it to a type 1 chain making a Type 1 H antigen.
FUT1 gene codes for a1,2-fucosyl transferase 1, what type of chain does this enzyme add fucose to?
It adds it to a type 2 chain making a Type 2 H antigen.
What blood group is an individual if no A or B antigen is attached to the H antigen?
They will be blood group O.
What mutation causes the bombay phenotype?
It is caused by a mutation in FUT1 therefore no H antigen expression on type 2 chains. This causes a lack of A and B antigens as they require H antigen to be expressed therefore the individual appears to be blood group O. Their serum will contain anti-A, anti-B and anti-H therefore can only receive blood from other bombay blood. This is shown as h/h.
Why does inactive FUT2 gene not lead to bombay phenotype?
This does not lead to bombay phenotype because this is the secretor gene which creates type 1 H antigens allowing expression within secretions such as saliva therefore does not effect the cells. Inactive FUT2 is shown as se/se.
How many subgroups of A antigen are there and what are they?
There are 5 groups called: A1, A2, A3, Ax and Ael. Over 99% are either A1 or A2 but these code for different transferases. A2 is less efficient in converting H therefore RBCs have 20-25% less A antigens than A1 cells.
What are the main antigens that are of concern in the Rh system in order of how immunogenic they are?
D, c, E, C and e.