37. Blood groups and transfusions

Question 1

What are autoantibodies?

Answer 1

Antibodies to self - react with antigens present on the person’s own cells

Question 2

What are alloantibodies?

Answer 2

Antibodies to something other than self - foreign material

Can be naturally occurring or immune derived

Question 3

What structures on the RBC determines the blood type of an individual?

Answer 3

RBC has a lipid bilayer at the surface
This contains sugar residues and proteins
Sugar residues - form one blood group system e.g. ABO
Protein - forms another blood group system e.g. Rhesus

Question 4

What is the blood type of an individual determined by?

Answer 4

Genes - determine what particular sugar or protein is produced - so what the blood group is

Question 5

What are antibodies?

Answer 5

Immunoglobulins in the plasma which react specifically with their antigen e.g. the A antigen and the anti-A antibody

Question 6

Are there antigens on a RBC?

Answer 6

Yes - red cell antigens at the surface can stimulate antibody formation

Question 7

When can alloantiboides to blood be dangerous?

Answer 7

Alloantibodies exposed to somebody else’s red blood cells e.g. in blood transfusion or pregnancy

Question 8

What are the antigens present on RBCs?

Answer 8

A and B

Question 9

If you have A or B antigens on your RBCs, what antibodies do you have?

Answer 9

A/B antigen - tend to have naturally occurring antibodies to the antigens that are missing e.g. if you are A - will develop anti-B antibodies

Question 10

What type of Ig are the antigens to red blood cells?

Answer 10

IgM or IgG

Question 11

What are the different ABO antigens/blood types and what antibodies do these individuals have?

Answer 11

A - has anti-b in the plasma
B - has anti-a in the plasma
O - has anti-a and anti-b in the plasma
AB - has NO ABO antibody in the plasma

Question 12

Define agglutinate (antibodies)

Answer 12

Antibodies will agglutinate to the relevant antigen to prevent it from binding to anything else/in an attempt to destroy it

Question 13

What will agglutinate the different ABO blood types?

Answer 13

Blood A - agglutinated by anti-A
Blood B - agglutinated by anti-b
Blood AB - agglutinated by anti-a and anti-b
Blood O - NOT AGGLUTINATED BY ANTI-A OR ANTI-B

Question 14

What is the universal blood type donor?

Answer 14

Blood type O - will not be agglutinated by antibodies - can be given to anyone requiring blood

Question 15

What is the universal blood type acceptor?

Answer 15

People with AB - can accept any blood type - they have no antibodies

Question 16

How can you determine what blood type someone is?

Answer 16

Look at their blood for the relevant antigen

Look at their blood plasma for the antibodies that are present

Question 17

What are the different rhesus blood types?

Answer 17

C or c
D or no D (no D is written as d)
E or e

Question 18

Are antibodies produced against the rhesus blood types?

Answer 18

Not naturally produced - will only be produced via the immune system
Produced if someone is exposed to the antigen through transfusion, pregnancy, transplantation

Question 19

What will the rhesus phenotype of CcDe be agglutinated by?

Answer 19

Anti-C
Anti-c
Anti-D
Anti-e

Question 20

What will the rhesus phenotype cdE be agglutinated by?

Answer 20

Anti-c
Anti-E
NOT BY ANTI-d - remember that d means ‘no D’ - there is no d antigen and so there is no d antibody

Question 21

Which rhesus antigen is the most clinically important and why?

Answer 21

D antigen
80% of people without the D antigen will develop anti-D if they are exposed to it
e.g. CcDEe - have the D antigen and so they are rhesus D positive
e.g. Cde/cde - do not have the D antigen and so these individuals are rhesus D negative

Question 22

What is haemolytic disease of the newborn? (HDN)

Answer 22

A rhesus negative mother will have anti-D antibodies
If they have a Rhesus positive baby - can lead to still birth or severe brain damage in the child - antibodies cross the placenta and destroy the foetal red cells

Question 23

How is HDN prevented?

Answer 23

Rhesus negative mothers carrying rhesus positive babies are given prophylactic anti-D antibodies

Question 24

What are the different types of blood transfusion that can be provided?

Answer 24

Whole blood - one unit as collected from donor
Red cells - unit with most of the plasma removed
Red cells in additive solution - unit with most plasma, white cells, platelets removed
Leucocyte-depleted red cells - 99.9% of white cells removes

Question 25

What are the risks of a blood transfusion?

Answer 25

Transmit infection
Alloimmunisation - antibody production which could compromise future transfusion
Incompatible transfusion
Iron overload from multiple transfusions
Circulatory overload

Question 26

What is the purpose of the indirect antiglobulin test?

Answer 26

Used to screen for atypical antibodies in the patient’s plasma