TM ABO Group

Question 1

ABO and H genes code for..

Answer 1

glycosyltransferases (enzymes)

= adds carbohydrates to type-2 paragloboside chain (Precursor Substance)

Question 2

What is the ABO type ?

Anti-A = 4+
Anti-B = 4+
A1 cells = 0
B cells = 0

Answer 2

AB

Question 3

What is the ABO type ?

Anti-A = 0
Anti-B = 0
A1 cells = 4+
B cells = 3+

Answer 3

O

Question 4

L-fucosyl transferase

Answer 4

• encoded by gene H
• adds L-fucose = H antigens

Question 5

N-acetyl-D-galactosaminyl

Answer 5

• encoded by gene A
• adds N-acetyl-D-galactosamine

Question 6

D- galactosyl

Answer 6

• encoded by gene B
• adds D-galactose

Question 7

T or F: Almost 100% of the population will inherit two H genes

Answer 7

TRUE;
only one H needs to be inherited for L-fucosyl transferase to be produced = adds L-fucose to the PS

Question 8

the __ antigen allows for other transferases to add sugars and form A and B antigens

Answer 8

H antigen

Question 9

What kind of molecules are ABO antigens ?

Answer 9

glycoproteins

Question 10

What are lectins ?

Answer 10

• proteins (found in nature) that bind specific carbs
• act as artificial Abs that bind certain antigens

Question 11

Ulex europaeus

Answer 11

Anti-H
- seeds have lectin that binds H

Question 12

Genotype for ABH secretors ?

Answer 12

• SeSe
• Sese

NOTE: only need one “Se” allele

Question 13

Describe secretors of ABH antigens

Answer 13

• 80% of population (SeSe, Sese)
• make soluble antigens found in plasma, sweat, tears, etc.

Question 14

ABO group with most amount of H

Answer 14

Type O

NOTE: H antigens have been added to PS

Question 15

who produces Anti-H ?

Answer 15

• people who did not inherit at least one H allele (only have PS on RBC membrances)
• Bombay blood group
• IgM & naturally occurring

Question 16

anti-H

Answer 16

• IgM
• naturally occurring*

*NOTE: IN BOMBAY, not in others

Question 17

IgM

Answer 17

naturally occurring

Question 18

IgG: naturally occurring or RBC-stimulated ?

Answer 18

RBC-stimulated

Question 19

What do the forward vs reverse group in ABO testing determine ?

Answer 19

Forward = tests antigens on the patient’s cells

Reverse = tests for ABO antibodies in patient plasma

Question 20

What do Bombay people type as ?

Answer 20

Type O

• must be transfused with Bombay blood due to anti-H in plasma

Question 21

How do we test for Bombay ?

Answer 21

1. test patient RBCs with anti-H lectin (Ulex europaeus) = will be 0 because Bombay don’t have H antigens at all
2. test for anti-H (which Bombay people should have) with O cells (which is rich in H) = positive !

Question 22

anti-A1

Answer 22

• naturally occurring
• cross-reacts with A1 cells
• cold, clinically insignificant IgM (not same properties as anti-A, -B)
• unexpected; only made by 2-5% of people; <10% of A2B

Question 23

Dolichus biflorus

Answer 23

anti-A1 lectin

Question 24

Who can make anti-A1 ?

Answer 24

• ONLY A2 people and A2B people
• NOT A1

Question 25

What is an auto-control ?

Answer 25

• 2 drops of patient plasma with 1 drop of patient cells = SHOULD NOT CLOT
• can be useful in resolving a discrepancy

Question 26

Cause: missing/weak antibodies (RG <2+)

Answer 26

• newborns <6 months
• seniors >70 years
• hypo/agammaglobulinemia

Question 27

How to resolve missing/weak antibodies (RG <2+)

Answer 27

• add more plasma (4 drops instead of 2) to cells to promote shift to right (4:1 ratio of plasma cells)
• incubate RT for 30 mins
• incubate at 4℃ (ABO reacts best in cold)

Question 28

Cause: extra antibodies

Answer 28

• irregular IgM alloantibodies (Lewis, P1, M, N)
• cold autoagglutinins (anti-I, -IH, -H, -IA, -IB)
• anti-A1
• rouleaux

Question 29

What are the extra irregular IgM alloantibodies ? How do you resolve them ?

Answer 29

• Lewis, P1, M, N
• naturally occurring IgM that some patients have; insignificant; read 4℃
• resolve by PRE-WARMING: use aliquot of plasma, drop of B cells, and pipette that have been warmed for 10 minutes = mix
• if all else fails, then identify Ab (ie. anti-M)

Question 30

What are cold agglutinins ? How do you resolve them ?

Answer 30

ie. anti-I
- clinically insignificant (mostly)
- autoAb
- IgM; naturally occurring
- resolve by PRE-WARMING

Question 31

How is anti-A1 resolved ?

Answer 31

• made by Type A2 or A2B individuals
• IgM; clinically insignificant; reacts in the cold
• autocontrol = 1+

Resolve by:
1. PRE-WARM plasma, cells and pipette for testing
2. investigate using lectin (Dolichus biflorus): true anti-A1 will be pos with A1 cells and neg with A2 cells
3. use A2 cells in reverse group testing

Question 32

What is rouleaux ? How is it resolved ?

Answer 32

• increased protein in the plasma (multiple myeloma, acute phase reactants)
• RG rxns will all be 1+, including auto-control
• resolve by doing SALINE REPLACEMENT = remove plasma, replace with 2 drops of saline, mix, spin read = rxn should now be 0

Question 33

Differentiate A1 vs A2 cells

Answer 33

• A1 will have a more efficient transferase (N-acetyl D galactosaminyl) = more A antigens on cells
• A1 cells have more branched carbohydrates

Question 34

If both parents are Type AB, why might the child not have any A or B antigens ?

Answer 34

The child is bombay (hh) = will Type as O

Question 35

In TM, what rxn strength is considered abnormal and requires follow-up ?

Answer 35

less than 2+

Question 36

Which antibodies are expected ?

Answer 36

• anti A, -B, -AB
• anti-H in bombay