TS1 Flashcards
What are the various human blood groups?
A
B
O
AB
What antigens do the various blood groups possess?
A - A
B - B
AB - A and B
O - Neither
What antibodies do the various blood groups produce?
A - anti-B
B - anti-A
AB - none
O - anti-A and anti-B
What is Landsteiner’s Law?
Anybody without a particular antigen automatically makes antibodies for the antigens they don’t possess.
Why are blood group antibodies different from other antibodies?
They are produced automatically, and do not require prior exposure to blood group antigens.
Normally the immune system meets an antigen and then in subsequent exposures, antibodies are made. The theory is that there are bacteria similar to A & B in our bodies and our bodies make antibodies to these very early in life.
What are blood group antigens?
Inherited determinants on red blood cells capable of stimulating an antibody response in someone lacking the antigen
What are blood groups?
Antigens encoded by the same gene or cluster of genes (inherited together) are assigned to a blood group
In what ways do blood group antigens differ?
Blood group antigens differ in their frequency, antigenicity and clinical significance
What are A and B antigens?
A and B antigens are carbohydrate groups built onto membrane proteins or lipids by glycosyl-transferase enzymes
Describe alleles A and B
Alleles A and B are antithetical alleles coding for enzymes which transfer CHO groups onto a precursor substance, H.
Antithetical allele’s means they are two forms of the same gene.
What is the purpose of the FUT1 gene?
FUT1 gene codes for L-fucosyltransferase which forms the H antigen
What is the purpose of the FUT2 gene?
FUT2 gene controls the secretor (Se) status
What does the A allele code for?
A allele codes for N-acetylgalactosaminyl transferase which forms the A antigen
What does the B allele code for?
B allele codes for D-galactosyl transferase which forms the B antigen
What does the O allele code for?
It doesn’t. O allele is a null (amorphic) allele of the ABO
gene which leaves the H antigen unmodified
What type of inheritance do A and B alleles display?
A and B alleles are co-dominant (i.e. both are expressed if they are inherited), and dominant over O
Who possesses the FUT1 gene?
Everyone has the FUT1 gene, that codes for the glycolipids on the cell surface, that A and B antigens adhere to.
How are the ABO surface antigens affected by which blood group is inherited?
Everybody starts off with a H antigen with a fucose at the end.
If you inherit the A blood group, you have an enzyme that puts a galnac onto this to form the A antigen.
In B this puts a gal on, to form the B antigen
In O, it remains unmodified and stays as FUC on its own.
What are the two main subgroups of A?
A^1 and A^2
What percentage of people have A^1?
80%
What percentage of people have A^2?
20%
What is the difference between A^1 and A^2?
A1 and A2 genes both code for N-acetylgalactosaminyl transferase enzymes
A2 enzyme is less efficient, converting less H substance to A antigen
Why are there fewer genotypes giving rise to A^2 groups?
A1 is dominant over A2, so the only genotypes giving
rise to A2 phenotype are A2A2 and A2O
What percentage of the population have group O blood types?
UK 46 Germany 43 Africans 49 Lapps 18 Bengalis 22 SA Indians 100 (exclusively O) Aborigines 44
