Blood Transfusion (haematology)

Question 1

Name the reagent used in a coombs test

Answer 1

Anti-human globulin (AHG)

Question 2

What is leucodepletion?

Answer 2

It is the removal or white blood cells in whole blood from the donor before transfusion.

Question 3

What happens if leucodepletion is not done before the transfusion? (5)

Answer 3

-There will be platelets, which contain HLA I and PLT antigens.
-There will also be white blood cells which contain HLA I and HLA II antigens.
-The issue is HLA II, because it presents those antigens to the repient, causing the recipient to produce Anti-HLA I and anti-PLT antibodies.
-That will cause the antibodies to attack the antigen hence destruct the platelets.
-Therefore, in leucodepletion where we do not have HLA II there is no presentation of the antigens, no antibodies produced hence no destruction of platelets.

Question 4

Why does the leucodepletion process work on lymphocytes as it does in other WBCs?

Answer 4

Lymphocytes are very small, so they pass through the filter.

Question 5

What is irradiation?

Answer 5

Treating blood (donor’s) with radiation in order to inactivate the lymphocytes.

Question 6

What happens during the transfusion if the donor’s blood is not irradiated? (4)

Answer 6

-So firstly we all have different HLA antigens, except for identical twins.
-So when transfusion occurs, the lymphocytes from the donor’s blood recognise the HLA antigens of the recipient as foreign and attacks them.
-Luckily the recipient’s lymphocytes are able to recognise the donor’s lymphocytes and they attack them before they degrade their antigens.
-But for patient with T-lymphocyte dysfunction or lymphopenia, their lymphocytes are not able to attack the donor’s lymphocytes, therefore the recipient’s HLA antigens gets degraded.

Question 7

Explain the ‘one way HLA match’ (3)

Answer 7

-This occurs when there is blood transfusion between people who are family.
-Let us say the donor has two HLA antigens that are the same e.g A2B7 and the recipient has one of it’s HLA antigens being A2B7 and a different one.
-The lymphocytes of the donor will recognise the different antigen and attack it, but instead of the lymphocytes of the recipient attacking back, they see the A2B7 antigen which they also have (not foreign) and they do not attack back.

Question 8

What are the complications associated with transfusion that present with fever? (7)

Answer 8

•Acute
-Acute haemolytic reaction
-Febrile reaction
-Transfusion related acute lung injury (TRALI)
-Bacterial contamination
•Delayed
-Delayed haemolytic reaction
-Transmission of viral diseases
-Transmission-associated graft versus host disease. (TA-GVHD)

Question 9

What are the transfusion associated complications that present without fever? (5)

Answer 9

•Acute
-Allergic reaction
-Anaphylactic reaction
•Delayed
-Alloimmunisation
-Post-transfusion purpura
-Iron overload