ABO blood group

Question 1

Which antigens and antibodies are produced in each of the ABO groups, and what is their distribution in the Australian population?

Answer 1

• A: A = a-B . 39%
• B: B = a-A . 11.5
• AB: A + B = N/a . 3.5%
• O: H = a-A,B . 46%

Question 2

Describe the general production of the ABO antigens

Answer 2

H, A, B Ag are produced by +ing single CHO residue (immunodominant) on precursor substance by glycosyltransferase
Type 2 precursor substance -> H Ag -> A or B Ag)

Question 3

Describe the sugars on the type 2 precursor substance

Answer 3

4. Gal (D-galactose)
5. AcGlu (N-acetylglucosamine)
6. Gal (D-galactose)
7. Glu (Glucose)
   RBC Membrane

Question 4

Describe the production of the H antigens

Answer 4

a-2-L-fucosytransferase adds L-fucose to terminal D-galactose on T2 precursor substance
4. Gal –––– L-fucose
3. AcGlu
2. Gal
1. Glu
RBC Membrane

Question 5

Describe the production of the A antigens

Answer 5

a-3-N-acetylgalactosaminyltransferase adds N-acetyl-D-galactosamine to terminal D-galactose on H Ag
4. Gal ==== L-fucose + N-acetyl-D-galactosamine
3. AcGlu
2. Gal
1. Glu
RBC Membrane
*NOTE: A Ag hides H Ag

Question 6

Describe the production of the B antigens

Answer 6

a-3-D-galactosyltransferase adds D-galactose to terminal D-galactose on H Ag
4. Gal ==== L-fucose + Gal
3. AcGlu
2. Gal
1. Glu
RBC Membrane
*NOTE: B Ag hides H Ag

Question 7

Describe the characteristics of ABO antibodies

Answer 7

• Naturally occuring: w/out prior exposure to RBC Ags but from same Ag.enic structure of gut bacteria
• usually IgM (a-A,B is IgG)
• bind complement
• react optimally @ RT
• clinically significant - can cause intravascular heamolysis => death

Question 8

Describe how an individual’s ABO group is

determined

Answer 8

• FWD ABO gp: patient’s cells reacted w/ known antiserum => ID Ag present on patient’s RBC
• RVS ABO gp: patient’s plasma reacted w/ known cells => ID Ab present in patient’s plasma

Question 9

What type of inheritance is ABO genes expressed?

Answer 9

autosomal co-dominant

• presnece of 1 allele = Ag expressed
• presence of 2 alleles = both Ag expressed