LA2 ABO Blood Group System

Question 1

Acute hemolytic transfusion reaction

Answer 1

Complication of transfusion associated with intravascular hemolysis, characterized by rapid onset
with symptoms of fever, chills, hemoglobinemia, and hypotension; major complications include irreversible shock, renal failure, and disseminated intravascular coagulation.

Question 2

Universal donor

Answer 2

Universal donor for RBC transfusions is group O; universal donor for plasma transfusions is group AB.

Question 3

Universal recipient

Answer 3

Universal recipient for RBC transfusions is group AB; universal recipient for plasma transfusions is group O.

Question 4

Forward grouping

Answer 4

Use commercially prepared anti-A and anti-B to test patient cells for A and B antigens.

Question 5

Reverse grouping

Answer 5

Use commercial A-cells and B-cells to test patient’s plasma for anti-A and anti-B.

Question 6

Landsteiner’s Law

Answer 6

Normal, healthy individuals will have ABO antibodies to the ABO antigens which are lacking on their red blood cells.

Question 7

Formation of H antigens

Answer 7

End-product of an enzymatic reaction: transferase enzymes promote attachment of immunodominant sugar (fucose) to precursor substance (4-sugar chain) on RBCs membrane.

Question 8

Immunodominant sugar fo A antigen

Answer 8

N-acetylgalactoseamine (“GalNac”)

Question 9

Immunodominant sugar for B antigen

Answer 9

D-galactose

Question 10

Immunodominant sugar for H antigen

Answer 10

Fucose

Question 11

When do ABO system antibodies start to present in the blood?

Answer 11

After ~4 months.

Question 12

At what age do ABO system antibodies reach their highest titre?

Answer 12

5-10 years

Question 13

What happens with ABO system antibodies as the people grow older?

Answer 13

ABO antibodies titre gradually declines with age.

Question 14

Clinical significance of ABO system antibodies

Answer 14

1) Very good at activating complement cascade and causing intravascular hemolysis -> AHTR (acute hemolytic transfusion reaction)
2) Can agglutinate RBC’s directly
3) Best at RT and don’t need incubation time, but also react at 37C (body temp)

Question 15

Frequencies of ABO blood types

Answer 15

Most common - O (~40%); then A, B; least common - AB (4-5%).

Question 16

Ulex europaeus

Answer 16

Plant lectin with specificity for the H antigen (reacts with H antigen on RBCs surface).

Question 17

How is reverse grouping related to forward grouping?

Answer 17

Reverse grouping is a control for forward grouping.

Question 18

Why reverse grouping is not done on infants younger than 4 months old?

Answer 18

Because they don’t have any ABO antibodies yet.

Question 19

Formation of A and B antigens

Answer 19

Transferase enzymes attach A or B immunodominant sugar to the H antigen on RBCs membrane.

Question 20

Anti-H

Answer 20

Ulex europaeus lectin. Usually used to test to see amount of H antigen on the patient’s RBCs.

Question 21

What immunoglobulin class are anti-A and anti-B?

Answer 21

IgM, with the exception in group O person - IgG

Question 22

How does the H antigen concentration vary in ABO phenotypes?

Answer 22

Group O - no sugars added, therefore all antigens remain H antigens. Group AB - most H antigens are converted to A or B antigens, therefore fewest number of H antigens left.

Question 23

Formation of ABO system antibodies

Answer 23

Produced as a result of exposure to environmental factors which have similar biochemical structures to the A and B antigens.

Question 24

Non-red cell stimulated antibodies

Answer 24

Antibodies produced without exposure to other person’s RBCs.

Question 25

Anti-A,B

Answer 25

Additional antibody made by group O individuals only. Reacts with A antigens and/or B-antigens.

Question 26

When performing ABO-typing, which stage of agglutination is enhanced by centrifuging the tests?

Answer 26

Lattice formation

Question 27

What is the minimum reaction strength which must be obtained in the forward ABO grouping to call it positive without further testing?

Answer 27

3+

Question 28

What is the minimum reaction strength which must be obtained in the reverse ABO grouping to call it positive without further testing?

Answer 28

2+

Question 29

What should be done if the result obtained in reverse ABO grouping doesn’t “match” forward ABO grouping for that patient?

Answer 29

Repeat both tests.

Question 30

Lectin

Answer 30

A protein derived from a plant which reacts with red cell antigens.

Question 31

Possible genotype for A group

Answer 31

AA or AO

Question 32

Possible genotype for B group

Answer 32

BB or BO

Question 33

What is a Bombay phenotype?

Answer 33

Phenotype corresponding to hh genotype (absence of H gene).

Question 34

What would be result of Ulex europaeus test with a Bombay phenotype blood?

Answer 34

Negative

Question 35

What would a Bombay phenotype look like in ABO forward testing?

Answer 35

Like group O. In Bombay phenotype, RBCs lack H antigens, so terminal sugars cannot be added to get A o B antigens.

Question 36

Which ABO antibodies does a Bombay phenotype person have?

Answer 36

Anti-A, anti-B, anti-A,B, and anti-H

Question 37

Who can become a donor for a Bombay phenotype person?

Answer 37

Only another Oh person:
- check siblings, rare donor banks
or - patient can make autologous donations for future use

Question 38

What are the typical reactions for a Bombay phenotype in ABO typing?

Answer 38

–A : 0 ; –B : 0 ; –A,B : 0 ; AC : 4+ ; BC : 4+ ; OC : 4+

Question 39

What would the phenotype be for AAhh genotype?

Answer 39

Oh - Bombay phenotype.