ABO System

Question 1

How many blood groups are there?

Answer 1

8

Question 2

what are the two systems used to classify blood

Answer 2

ABO system and Rhesus system

Question 3

What are the 4 groups in the ABO system

Answer 3

O, A, B and AB

Question 4

What is the most common blood type in Ireland?

Answer 4

O+

Question 5

What is the least common blood group in Ireland?

Answer 5

AB-

Question 6

Who came up with the ABO system>

Answer 6

Karl Landsteiner in 1901

Question 7

Write a sentence to describe the relationship between antigens on red cells and plasma/serum antibodies

Answer 7

The plasma contains the opposite antibody to the antigen found on the red cell. i.e A antigen on red cell = B antibody in plasma/serum

Question 8

What type of antibody are ABO antibodies?

Answer 8

IgM

Question 9

When might a Haemolytic Transfusion Reaction occur?

Answer 9

when a patient has been transfused with the wrong blood type, usually due to mislabeling of a blood sample, mis-grouping of blood donations or transfusing the wrong patient

Question 10

What chromosome are the A, B and O alleles found on?

Answer 10

chromosome 9 at the ABO locus

Question 11

Which chromosome are the H and h alleles found on?

Answer 11

chromosome 19

Question 12

what are olgiosaccharide chains?

Answer 12

are attached to the membrane of the RBCs, and are the foundation blocks for the building of the ABO blood group antigens

Question 13

What does the H gene do?

Answer 13

codes for a transferase enzyme which adds fucose to olgiosaccharide chains on the red cell membrane.

Question 14

What is the function of the H antigen

Answer 14

is the precursor material on which A and B antigens are built

Question 15

How are the A and B antigens formed?

Answer 15

A and B genes code for a transferase enzyme. This acts on the H precursor antigen which produces the A and B antigen

Question 16

the O gene is an amorph, what does this mean?

Answer 16

it does not encode a functional enzyme, meaning no detectable antigen is produced.

Question 17

does group O contain more or less of H antigen than A, B or AB groups?

Answer 17

they have more H antigen

Question 18

what enzyme does the A gene code for?

Answer 18

alpha 1,3-Nacetyl-galactosaminyltransferase

Question 19

how does alpha 1,3- Nacetyl-galactosaminyltransferase work?

Answer 19

it uses H antigen as a substrate, and catalyses the addition of the sugar N- acetyl galactosamine to the last galactose of the olgiosaccharide chain to produce A antigen.

Question 20

what must be present for the A enzyme to produce the A antigen?

Answer 20

H antigen

Question 21

What enzyme does the B gene code for?

Answer 21

alpha 1,3-galactosyltransferase

Question 22

how does alpha 1,3-galactosyltransferase work to produce B antigen?

Answer 22

Uses H antigen as a substrate, and catalyses the addition of the sugar D-galactose to the final galactose of the olgiosaccharide chain to produce B antigen

Question 23

What must be present in order for the B enzyme to produce B antigen?

Answer 23

H antigen

Question 24

What is the possible genotype if you have A blood type?

Answer 24

A/A or A/O

Question 25

What is the possible genotype if you have B blood type?

Answer 25

B/B, B/O

Question 26

What is the possible genotype if you have AB blood type?

Answer 26

A/B

Question 27

What is the possible genotype if you have O blood type?

Answer 27

O/O

Question 28

Write a note on the genetic profile of the Bombay blood group

Answer 28

This group is quite rare. They are homozygous for the h allele, meaning they lack the H gene. They cannot form the H antigen (precursor of A and B antigens).

Question 29

which blood type does Bombay O group as?

Answer 29

Groups as type O as it is not agglutinated by anti A or B, or anti H

Question 30

are ABO antibodies naturally occurring or immune occurring?

Answer 30

naturally occurring but are thought to be stimulated by substances that are everywhere in nature (environmental antigens)

Question 31

How soon after birth can ABO antibodies be found?

Answer 31

3-6 months

Question 32

Are all ABO antibodies IgM?

Answer 32

Most are IgM, but some people have IgG at low levels

Question 33

What is direct agglutination?

Answer 33

A test which looks for serum antibodies

Question 34

at what temperatures do antibodies react at?

Answer 34

4-22 degrees centigrade but can also react at body temperature as they are potent

Question 35

where might an absence of ABO antibodies be found?

Answer 35

new borns, infants, patients with hypogammaglobinaemia or patients in chemo/radium treatment. May also be in elderly patients as levels may fall with increased age.

Question 36

what is a gammaglobin

Answer 36

an antibody

Question 37

Is it mandatory to use anti AB in cell grouping?

Answer 37

no

Question 38

Why might forward and reverse grouping not match?

Answer 38

If an infant <6 months old blood is tested

Question 39

Why should reverse grouping not be carried out on infants <6 months?

Answer 39

They don't have any anti-A or anti-B antibodies

Question 40

Which groups of people have weak reactions for reverse grouping?

Answer 40

Elderly, immunocompromised and newborns

Question 41

How does antibody specificity work?

Answer 41

The variable region (sequence of amino acids) corresponds to specific antigen