Blood Transfusion

Question 1

What glycoprotein and fructose stem is common to everyone?

Answer 1

H stem

Question 2

What are A and B antigens?

Answer 2

The A and B antigens are made by the addition of a sugar residue onto the common glycoprotein and fructose stem (H stem)

Question 3

What does the A gene encode?

Answer 3

An ENZYME that adds N-acetyl galactosamine to the H stem

Question 4

What does the B gene encode?

Answer 4

An ENZYME that adds galactose to the H stem

Question 5

Describe the inheritance pattern of the ABO blood groups.

Answer 5

A and B genes are codominant
O is ‘recessive’ because it doesn’t code for anything at all
So you need to be homozygous for O (OO) to be in blood group O

Question 6

Which antibodies would someone in blood group A possess? Why?

Answer 6

Anti-B antibodies because each person produces antibodies against any antigen that is NOT present on their own red cells.

Question 7

What class of immunoglobulin are these antibodies?

Answer 7

IgM

They are naturally occurring (nearly from birth)

Question 8

What would happen if someone with anti-B antibodies was given B-positive blood?

Answer 8

The anti-A/anti-B antibodies are complete antibodies meaning that it fully activates the complement cascade to cause haemolysis of red cells
This is often FATAL
It can lead to cytokine storm, lysis, cardiovascular collapse and death

Question 9

In the laboratory, what would you see if you were to mix the plasma of someone of blood group A with the red cells of someone in blood group B?

Answer 9

Agglutination

Question 10

What is done before transfusion to check that the donor blood and the recipient’s blood is compatible?

Answer 10

A blood sample is taken from the patient and the ABO blood group is determined (test with anti-A and anti-B antibodies)
Select a donor unit of the same group
CROSS-MATCH: patient’s serum is mixed with donor red cells – it should NOT react (if it reacts then it shows that it is incompatible)

Question 11

Which rhesus antigen is the most important?

Answer 11

RhD

Question 12

Describe the inheritance pattern of the RhD antigen.

Answer 12

Autosomal Dominant

RhD codes for the D antigen

Question 13

Describe the relative proportions of RhD positive and RhD negative individuals within the population.

Answer 13

RhD positive = 85%

RhD negative = 15%

Question 14

What can happen when RhD negative people are exposed to RhD positive blood?

Answer 14

They become sensitised and can make anti-D antibodies

Question 15

What type of antibody are anti-D antibodies?

Answer 15

IgG

Question 16

What is haemolytic disease of the newborn?

Answer 16

If an RhD negative mother generates anti-D antibodies following pregnancy with a RhD positive foetus, then if the next foetus is RhD positive, the mother’s anti-D antibodies (IgG) can cross the placenta and cause haemolysis of foetal red blood cells.
If severe this can cause hydrops fetalis and death.

Question 17

Why are the red cells concentrated and the plasma removed?

Answer 17

It allows you to avoid fluid overloading, which can precipitate heart failure, when giving someone red cells

Question 18

What three components is blood first separated into via centrifugation?

Answer 18

Plasma
Platelets (and white cells)
Red Cells

Question 19

What is fresh frozen plasma (FFP) and what does it contain?

Answer 19

If the plasma is frozen within 6 hours of donation then all the coagulation factors are preserved – this is fresh frozen plasma (FFP)

Question 20

How many donors does it take to make one unit of red blood cells?

Answer 20

1

Question 21

How are red blood cells stored and what is their shelf life?

Answer 21

They are packed cells with the plasma removed and they are stored in a 4-degree fridge
Shelf-life = 5 weeks

Question 22

How many donors does it take to make one unit of FFP?

Answer 22

1 (300 ml)

Question 23

How is FFP stored and what is its shelf life?

Answer 23

It is stored at -30 degrees Shelf-life = 2 years

Question 24

What are the indications for FFP?

Answer 24

Bleeding and abnormal coagulation test results (PT and APTT)
Reversal of warfarin (e.g. for urgent surgery) – this is because warfarin inhibits factor 2, 7, 9 and 10