L.2 ABO Blood Group system

Question 2

Who first demonstrated the ABO blood group system?

Answer 2

Karl Landsteiner in 1900

Question 3

What is the fourth blood group that was demonstrated in 1902?

Answer 3

AB

Question 4

How are ABO antibodies formed in the serum?

Answer 4

Naturally, stimulated by encountering ‘missing’ ABO blood group antigens in food or microorganisms

Question 5

What types of immunoglobulins can ABO antibodies be?

Answer 5

IgG or IgM

Question 6

What happens when anti-A and anti-B antibodies bind to RBCs?

Answer 6

They activate the complement cascade, lysing the RBCs (intravascular haemolysis)

Question 7

What can acute haemolytic transfusion reaction be caused by?

Answer 7

Intravascular haemolysis due to ABO antibodies

Question 8

At what age do newborns start making antibodies?

Answer 8

3-6 months

Question 9

How do ABO antibodies change with age?

Answer 9

They weaken with age

Question 10

On which chromosome is the ABO gene located?

Answer 10

Chromosome 9

Question 11

What do the functional A and B alleles encode?

Answer 11

A and B glycosyltransferases

Question 12

What does the O allele encode?

Answer 12

An enzyme with no function, resulting in no A or B antigen production

Question 13

What are the antibodies for antigens A and B termed?

Answer 13

Anti-A and anti-B

Question 14

What occurs when the corresponding antigen and antibody are mixed?

Answer 14

They form antigen-antibody complexes, agglutinating the blood

Question 15

Fill in the blank: The ABO antibodies in the serum can be _______.

Answer 15

IgG or IgM

Question 16

True or False: The corresponding antigen and antibody can be found in the same individual.

Answer 16

False

Question 17

What are Anti-A/Bs clinically significant for?

Answer 17

They fix complement and cause rapid intravascular hemolysis, triggering an acute haemolytic transfusion reaction.

This reaction can lead to disseminated intravascular coagulation, shock, acute renal failure, and death.

Question 18

What does Landsteiner’s rule state?

Answer 18

Healthy individuals possess ABO antibodies to the ABO blood group antigens absent from their RBCs.

Question 19

Define ‘locus’ in genetics.

Answer 19

Site at which a gene is located on a chromosome.

Question 20

What is an allele?

Answer 20

Alternative forms of a gene found at each locus.

Question 21

What are antithetical antigens?

Answer 21

Antigens produced by different alleles at the same locus.

Question 22

What does it mean if a gene is polymorphic?

Answer 22

It can have multiple different alleles at a single locus.

Question 23

What type of genes are A and B genes considered?

Answer 23

Dominant.

Question 24

What type of gene is the O gene?

Answer 24

Recessive or silent.

Question 25

What does 'recessive' mean in genetics?

Answer 25

A gene is expressed only when inherited by both parents.

Question 26

Define 'codominant' in the context of genetics.

Answer 26

Equal expression of two different alleles.

Question 27

What is an example of codominance in blood groups?

Answer 27

Blood group antigens are codominant.

Question 28

What does 'dominant' mean in genetics?

Answer 28

A gene that is expressed over another gene.

Question 29

What is an example of a dominant gene in blood types?

Answer 29

A antigen gene expressed over O gene.

Question 30

What are amorphic genes?

Answer 30

Genes that do not express a detectable product.

Question 31

Fill in the blank: The O gene is an example of _______.

Answer 31

amorphic genes.

Question 32

What genes influence ABO antigens?

Answer 32

ABO, H, Se ## Footnote All these genes are found on chromosome 19.

Question 33

What is controlled by the H gene?

Answer 33

The presence/absence of the ABO antigens on the RBC membrane.

Question 34

What influences the presence/absence of ABO antigen in secretions?

Answer 34

The Se gene.

Question 35

What alleles does the H gene encode?

Answer 35

H and h alleles ## Footnote h is an amorph.

Question 36

What is the genotype of individuals with the Bombay phenotype?

Answer 36

hh genotype.

Question 37

What antibodies are found in Bombay individuals?

Answer 37

Anti-H, anti-A, anti-B.

Question 38

What is the consequence of the antibodies in Bombay individuals?

Answer 38

Incompatibility with all other RBCs except those from another Bombay individual.

Question 39

What alleles does the Se gene encode?

Answer 39

Se and se alleles.

Question 40

What is a person who inherits identical alleles called?

Answer 40

Homozygous.

Question 41

What is a person who inherits different alleles called?

Answer 41

Heterozygous.

Question 42

What is the H antigen?

Answer 42

A basic precursor structure for several RBC antigens, including A, B, and H.

Question 43

What is the H antigen attached to?

Answer 43

A protein or lipid carrier molecule.

Question 44

What does the H antigen serve as?

Answer 44

The foundation for the A and/or B antigens.

Question 45

What does the H locus encode?

Answer 45

An α1,2 Fucosyltransferase called FUT 1.

Question 46

What does the A locus encode?

Answer 46

An α1,3 N-Acetylgalactosaminyl transferase.

Question 47

What does the B locus encode?

Answer 47

An α1,3 Galactosyltransferase.

Question 48

What does the Secretor gene encode?

Answer 48

An α1,2 Fucosyltransferase called FUT 2.

Question 49

How do the A and B alleles differ from each other?

Answer 49

By seven nucleotide substitutions.

Question 50

How many of the nucleotide substitutions in A and B alleles translate into different amino acids?

Answer 50

Four.

Question 51

What is the difference between the O allele and the A allele?

Answer 51

Deletion of guanine at position 261.

Question 52

What does the deletion in the O allele cause?

Answer 52

A frameshift resulting in a different protein that lacks enzymatic activity.

Question 53

What is the Bombay phenotype?

Answer 53

A rare phenotype of H-deficient RBCs where individuals do not produce H antigen, A, or B antigens ## Footnote Individuals with this phenotype have anti-A, anti-B, and anti-H antibodies and are at high risk for acute hemolytic transfusion reactions.

Question 54

What happens to individuals who are homozygous for null alleles at the H locus?

Answer 54

They do not produce H antigen and cannot produce A and B antigens ## Footnote Their serum contains anti-A, anti-B, and potent anti-H antibodies.

Question 55

What is the function of the Se locus?

Answer 55

It encodes a specific fucosyltransferase that produces H antigen in bodily secretions ## Footnote This enzyme is expressed in secretory tissues like salivary glands and gastrointestinal tract.

Question 56

What defines a 'secretor'?

Answer 56

Individuals with at least one copy of the Se gene (Se/Se or Se/se) who secrete H antigen ## Footnote They can process H antigen into A and/or B antigens depending on their ABO genotype.

Question 57

What is the genotype of a non-secretor?

Answer 57

se/se ## Footnote Non-secretors cannot produce a soluble form of H antigen and hence do not produce A and B antigens.

Question 58

What percentage of people are secretors?

Answer 58

75% ## Footnote Majority of the population has at least one functional Se gene.

Question 59

What are the two most important subgroups of A blood type?

Answer 59

A1 (80%) and A2 (20%) ## Footnote They are encoded by two separate genes and differentiated by the lectin Dolichos biflorus.

Question 60

How can A1 and A2 subtypes be differentiated?

Answer 60

By reacting red cells with the lectin Dolichos biflorus (Anti-A1) ## Footnote This lectin has specificity for A1 antigens.

Question 61

What plasma can Group O receive?

Answer 61

O, A, B, or AB Octaplas ## Footnote Group O is considered universal for plasma transfusions.

Question 62

What plasma can Group B receive?

Answer 62

B, AB, or A Octaplas ## Footnote Group B can receive plasma from its own type or AB.

Question 63

What plasma can Group A receive?

Answer 63

A, AB, or B Octaplas ## Footnote Group A can receive plasma from its own type or AB.

Question 64

What plasma can Group AB receive?

Answer 64

AB Octaplas ## Footnote Group AB is the universal recipient for plasma.

Question 65

What platelets can Group O receive?

Answer 65

O, A, B, or AB ## Footnote Group O is least preferable for platelets except to another Group O.

Question 66

What platelets can Group B receive?

Answer 66

B, A, or AB ## Footnote Group B can receive platelets from its own type or AB.

Question 67

What platelets can Group A receive?

Answer 67

A, B, or AB ## Footnote Group A can receive platelets from its own type or AB.

Question 68

What platelets can Group AB receive?

Answer 68

AB, A, or B ## Footnote Group AB can receive platelets from any blood type.