ABO Blood Group System

Question 1

What are the major blood groups of the ABO system?

Answer 1

A, B, AB, and O

Question 2

What is the function of blood groups?

Answer 2

• Compatibility testing
• Blood banking
• Ab screening
• Pre-transfusion testing
• Transfusion and transplant therapy

Question 3

What is the Landsteiner’s law?

Answer 3

#1: If an Ag is present on the RBC surface, the corresponding Ab must be absent in the plasma/serum.
#2: If an Ag is absent on the RBC surface, the corresponding Ab must be present in the plasma/serum

Question 4

What is the Landsteiner’s law?

Answer 4

1: If an Ag is present on the RBC surface, the corresponding Ab must be absent in the plasma/serum.

Question 5

What is the difference between forward and reverse blood grouping?

Answer 5

• Forward: Use known antibodies to test for antigens on the RBC surface of the patient
• Reverse: Use known antigens to test for antibodies in the plasma/serum of the patient

Question 6

How are ABO antigens coded for in DNA?

Answer 6

Genes coding for ABO antigens does not code for the antigens as a protein, but do coded for enzymes that will activate a sugar molecule that will attach to an oligosaccharide molecule to form a carbohydrate structure as the antigen.

Question 7

Explain the biochemistry for the formation of H-antigen.

Answer 7

• Chromosome 19 (H-Locus)
• H-gene form FUT-1
• Fucose bind to oligosaccharide molecule
• H-Antigen (precursor substance)

Question 8

Explain the biochemistry for the formation of A-antigen.

Answer 8

• Chromosome 9
• Gene expression
• Enzyme: N-Acetyl-D-Galactosaminyl-Transferase
• N-Acetyl-Galactosamine
• A-Antigen

Question 9

Explain the biochemistry for the formation of B-antigen.

Answer 9

• Chromosome 9
• Gene expression
• Enzyme: D-Galactosaminyl-Transferase
• D-Galactose
• B-Antigen

Question 10

Explain the biochemistry for the formation of O-antigen.

Answer 10

• Chromosome 9
• Gene expression
• A protein product with no enzymatic activity
• H-Antigen

Question 11

What is the relationship between H gene and ABO gene?

Answer 11

• H gene forms H-Antigen required for formation of A and/or B antigen coded for by ABO genes
• Inherited in Mendelian fashion
• ABO and H gene expression does not result in direct production of antigens

Question 12

Where can secretions of ABH substances be found on?

Answer 12

-All tissue cells with the Se gene or Se-antigen

Question 13

Which blood groups express the most H-antigen in decreasing and increasing order?

Answer 13

Decreasing: O > A2 > A2B > B > A1 > A1B
Increasing: A1B < A1 < B < A2B < A2 < O

Question 14

What is the difference between secretors and non-secretors?

Answer 14

• Secretors: Individuals w/ soluble ABH antigens in their secretions due to inheritance of the Se-gene (SeSe or Sese)
• Non-secretors: Individuals w/ no A and/or B antigens in their secretions due to no inheritance of the Se-gene (sese)

Question 15

What is the Bombay and Para-Bombay phenotype?

Answer 15

• Bombay:

- Para-Bombay:

Question 16

What is the Bombay and Para-Bombay phenotype?

Answer 16

• Bombay: Individuals who inherited the hh-genotype and do not produce the H-antigen, and therefore cannot produce A and /or B antigen. They also lack the Se-gene and does not have ABH antigens in their secretions.
• Para-Bombay: Individuals that did not inherit the H-gene, but did inherit the Se-gene (SeSe or Sese).

Question 17

Explain the following Bombay paternity cases:

Wife (AO) and Husband (AB) and Affair (OO), Child is OO

Answer 17

The wife and husband both inherited a single dose of the H-gene (Hh) and thechild inherited hh, making him/her unable to produce A and/or B antigen, despite inheriting A or B alleles.

Question 18

What is a subgroup?

Answer 18

A phenotype with variations in its structure or number of antigens

Question 19

What are the different subgroups in blood group A and AB?

Answer 19

• A1, A2

- A1B, A2B

Question 20

How are subgroups identified?

Answer 20

By adsorption and elution techniques to detect antigens on RBC surfaces in the lab

Question 21

What is a lectin?

Answer 21

Protein with Ab specificity originating from seed extracts of plants

Question 22

What is the function of a lectin?

Answer 22

Used to distinguish subtypes of various ABO blood groups

Question 23

What is the AB-trans effect?

Answer 23

Inheriting both AB genes from 1 parent carried on different chromosomes.

Question 24

What is the AB-cis effect?

Answer 24

Inheriting both AB genes from 1 parent carried on a single chromosome.

Question 25

What is a high titer?

Answer 25

Ab that can still cause agglutination after the highest dilution.

Question 26

What is a universal donor?

Answer 26

Individuals who have safe blood which can be transfused into any recipient of the ABO system.

Question 27

What is a universal recipient?

Answer 27

Individuals that have both A1 and B antigens on their RBC surface and does not have ABO antibodies in their serum and can receive blood from any donor of the ABO system.

Question 28

What is the clinical significance of ABO in HTR’s?

Answer 28

• Transfusion of A blood into group B patients will be disastrous
• Anti-A in B blood will react with A antigen on the donor RBCs and destroy them and anti-B in A blood will react with B antigen on the recipient RBCs and destroy them, causing activation of intravascular complement
• Lysis and RBC destruction
• HTR: Shock, acute renal failure, DIC, death.

Question 29

What is the clinical significance of ABO in HDFN’s?

Question 30

What is the clinical significance of ABO in HDFN’s?

Answer 30

• If a mother is O and is pregnant with a child who is blood group A, the mother will produce IgG anti-B which will cross the placenta and destroy the fetal RBCs.
• This destruction of RBCs result in haemolysis and unconjugated bilirubin to be in the fetal blood stream, which will then lead to kernicterus and brain damage.
• Haemolysis also lead sever anaemia and subsequently to cardiac failure and generalized edema (erythroblastosis faetalis).