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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?

N-acetyl-galactosaminyl transferase.


What enzyme does the B allele code for?

D-galactosyl transferase.


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.


RBCs without any Rh proteins are stomatocytic and spherocytic which leads to haemolytic anaemia why does this happen?

Rh proteins are crucial to the membrane of RBCs as they mediate interatactions with the cytoskeleton and have a role in ammonia transport.