Abo blood group _ Amanda

Question 1

Landsteiner’s Law

Answer 1

“If an antigen is present on the RBC of an individual, the corresponding antibody must be absent in the plasma of that individual and vice-versa.”

Question 2

Landsteiner’s Law example

Answer 2

Individual with A antigen on their RBC, hence blood group A, will have anti-B in their plasma

Question 3

Where is the ABO locus located?

Answer 3

ABO locus located on chromosome 9

Question 4

What deletion causes a frame shift resulting in the group O phenotype?

Answer 4

Deletion at residue 261 causes a frame shift

Question 5

How many allelic forms does the ABO locus have?

Answer 5

3: A, B, and O

Question 6

What do the A and B alleles each encode?

Answer 6

Glycosyltransferase that catalyses the final step in the synthesis of the A and B antigen, respectively

Question 7

What is the expression of A and B dependent upon?

Answer 7

A precursor H substance

Question 8

What do group O individuals lack?

Answer 8

Active enzyme

Question 9

Where is the H gene (FUT) located?

Answer 9

Chromosome 19

Question 10

What does H gene code for?

Answer 10

• inherited independently
• codes for an enzyme that converts carbohydrate precursors into H substance

Question 11

What do the A and B genes code for?

Answer 11

• specific enzymes that convert H substance into A and B antigens

Question 12

How is the blood group O achieved in an individual?

Answer 12

O gene produces an inactive transferase so H substance persists unchanged

Question 13

Type-1 chain basic precursor for ABH antigens

Answer 13

Beta (1-3) linkage

Question 14

Type- 2 chain basic precursor for ABH antigens

Answer 14

Beta (1-4) linkage

Question 15

What enzyme is involved in the formation of H antigen?

Answer 15

L Fucosyl Transferase enzyme (product of H gene)

Question 16

What enzyme is involved in the formation of the A antigen?

Answer 16

N-acetylgalactosaminyl transferase (product of A gene)

Question 17

What enzyme is involved in the formation of the B antigen?

Answer 17

D-galactosyl transferase (product of B gene)

Question 18

Why do Group O invidiuals have more H antigen than the other groups?

Answer 18

O gene is a silent allele.
Does not alter the structure of the H substance, so more H antigen sites

Question 19

What is the Bombay phenotype ?

Answer 19

Individuals whose RBCs lack the H antigen.
Described as Ohh

Question 20

Why does the Bombay phenotype RBCs also lack A and B antigens?

Answer 20

A and B antigens cannot be formed without the H antigen precursor

Question 21

What is the result of the Bombay phenotype?

Answer 21

O phenotype- since lack of A and B antigens
Produce anti-H

Question 22

Leucocytes

Answer 22

Lymphocytes acquire A, B and H antigens from the plasma of secretors

Question 23

Granulocytes and monocytes

Answer 23

Don’t express ABH antigens

Question 24

Platelets

Answer 24

Express ABH antigens on glycolipipds and the platelet glycoproteins

Question 25

Where is Blood group O frequency highest and lowest?

Answer 25

Highest- Nigeria Lowest- India

Question 26

Where is Blood group A frequency highest and lowest?

Answer 26

Highest- Turkey, Denmark and France Lowest- Nigeria

Question 27

Where is Blood group B frequency highest and lowest?

Answer 27

Highest- Pakistan Lowest- Australia, Denmark, France and USA

Question 28

Where is Blood group AB frequency highest and lowest?

Answer 28

Highest- India Lowest- Iran

Question 29

Blood group antibodies can be classified into:

Answer 29

Non-immune (Naturally occurring) Immune antibodies - cold and warm

Question 30

What are naturally occurring antibodies usually?

Answer 30

IgM (cold)

Question 31

What are non-immune antibodies

Answer 31

-ABO -Predominantly IgM although some IgG - produced early in neonatal period following colonisation of gastrointestinal system with bacteria

Question 32

What are immune antibodies?

Answer 32

- develop in response to the incompatible red cells- by transfusion or transplacental passage during pregnancy - antibodies commonly IgG, although some IgM

Question 32

What immune antibodies are the only one capable of transplacental passage from mother to foetus?

Answer 32

IgG

Question 33

What is an important immune antibody?

Answer 33

Rhesus antibodies, especially anti-D

Question 34

What serological methods are used in ABO blood grouping?

Answer 34

- test patient red cells with known antibodies for presence of A or B antigens (cell or forward group) - test patient’s serum for presence of Anti A and/or Anti-B antibodies by testing against cells of known red cell phenotype ( serum or reverse group)

Question 35

Molecular typing techniques?

Answer 35

Identification of gene sequences on chromosome 9 that confer ABO phenotype - not widely used currently due to the multiple genetic variations that phenotypically give rise to the A, B, AB and O groups

Question 36

ABO incompatibility

Answer 36

- the rapid intravascular haemolysis which occurs in ABO incompatible transfusions can precipitate severe disseminated coagulation (DIC), prolonged hypotension, acute uraemia, and event death

Question 36

Why are ABO antibodies of major clinical significance?

Answer 36

- naturally occurring and found universally - highly reactive, complement activating - transfusing a patient with the incorrect ABO blood group may have fatal consequences - incompatible donor red cells may be rapidly destroyed by anti-A or anti-B antibody in the recipients plasma

Question 37

What shoul blood grouping and identifying compatible blood components prevent?

Answer 37

Adverse transfusion reactions caused by ABO antibodies, however, clerical error can result in the “wrong blood” being transfused into a patient, an error which can result in patient death

Question 38

Serological compatibility testing

Answer 38

The patients plasma, containing antibodies, is tested against the red cells of the donor to determine if there is going to be a reaction

Question 39

Electron issue compatibility testing

Answer 39

- for patients who don’t have any history of having red cells antibodies and don’t have any unexpected antibodies in their current plasma sample - patients and donors are matched electronically for ABO and RhD with no physical cross match performed

Question 40

Antibody screening - blood group of patient is determined and screened for atypical antibodies

Answer 40

If antibody screen positive- crossmatched If antibody screen negative- electronic issue If blood is required before cross matching can take place, group O is given