ABO subgroups

Question 1

Describe the serological differences between the A subgroups, focusing on the A1, A2, A3, and Ax subgroups*(is that and correctly?)

Answer 1

• A1: a-B Ab 4+
• A2: “ “ “ & a-A 1+
• A3: sometimes produce a-A
• Ax: sometimes produce a-A
• all contain a-B Ab

Question 2

describe the bombay blood group

Answer 2

• not have ≥1 H allele = hh phenotype
• lack FUT1 (H) gene => not produce H Ag
  = anti -H, -A, -B Abs

Question 3

how do you screen blood from bombay blood group & what’s the suitable blood to give them

Answer 3

a) Ulex europeus (lectin) - clumps H Ag, so expect neg rxn bc no H Ag
b) transfused w/ blood from other Bombay individuals

Question 4

describe the para-bombay blood group

Answer 4

• Weak / no expression of H Ag
• weak expression of A / B Ag if person produces A / B transferase
• Anti-H weaker than bombay

Question 5

formation of para-bombay blood groups*(dc makes sense after revising)

Answer 5

• inactive FUT1 gene, active FUT2 (Se) gene => Type 1 H susbstance produced

Question 6

Explain the difference between an adsorption and an elution

Answer 6

• Adsorption: plasma Ab bind to Ag on RBC (step 1)

- Elution: dissociate Ab (bound on Ag) measure the presence of the Ab bound

Question 7

Describe how Dolichos biflorus (lectin) are used in transfusion science

Answer 7

Identify A2 subgroup bc

• A1 c = agglutinate
• A2 c = not agglutinate

Question 8

What it meant by the term “mixed-field agglutination”?

Answer 8

• Some RBC not agglutinated
• Some RBC agglutinated
  => see 2 lines on CAT = 4+ & 0 rxn grades seen

Question 9

how to distinguish A1 & A2 subgroups

Answer 9

Dolicous biflorus (anti-A1)

• A1 = pos
• A2 = neg

Ulex Europeus (anti-H)

• A1 = neg
• A2 =pos

Question 10

Describe the general production of the ABO antigens

Answer 10

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 11

Describe the sugars on the type 2 precursor substance

Answer 11

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

Question 12

Describe the production of the H antigens

Answer 12

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 13

Describe the production of the A antigens

Answer 13

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 14

Describe the production of the B antigens

Answer 14

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 15

how are A1 & A2 Ag differnet from each other

Answer 15

A1 = N-acetyl-D-galactosamine
A2 = mutant a-3-N-acetyl-D-galactosaminyltransferase = less efficient in converting H Ag -> A Ag = less A Ag

Question 16

difference b/w type 1 & type 2 precursor substance

Answer 16

Type 1: H Ag secreted from secretory tissues

Type 2: H Ag found only on RBC surface

Question 17

difference b/w FUT1, FUT2, FUT3

Answer 17

• FUT1 (H) > encodes α-4-L-fucosyltransferase = H Ag
• FUT2 (Se) > encodes for a-1,4-fulcosyltransferase = secretory ABO Ag
• FUT3 (Le) > encodes for a-1,4-fucosyltransferase = Le Ag

Question 18

What’s lectin?

Answer 18

• made from plant/seed extracts

- act like Abys - bind to specific sugar residues = agglutinate RBC