37. Blood groups and transfusions Flashcards
What are autoantibodies?
Antibodies to self - react with antigens present on the person’s own cells
What are alloantibodies?
Antibodies to something other than self - foreign material
Can be naturally occurring or immune derived
What structures on the RBC determines the blood type of an individual?
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
What is the blood type of an individual determined by?
Genes - determine what particular sugar or protein is produced - so what the blood group is
What are antibodies?
Immunoglobulins in the plasma which react specifically with their antigen e.g. the A antigen and the anti-A antibody
Are there antigens on a RBC?
Yes - red cell antigens at the surface can stimulate antibody formation
When can alloantiboides to blood be dangerous?
Alloantibodies exposed to somebody else’s red blood cells e.g. in blood transfusion or pregnancy
What are the antigens present on RBCs?
A and B
If you have A or B antigens on your RBCs, what antibodies do you have?
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
What type of Ig are the antigens to red blood cells?
IgM or IgG
What are the different ABO antigens/blood types and what antibodies do these individuals have?
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
Define agglutinate (antibodies)
Antibodies will agglutinate to the relevant antigen to prevent it from binding to anything else/in an attempt to destroy it
What will agglutinate the different ABO blood types?
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
What is the universal blood type donor?
Blood type O - will not be agglutinated by antibodies - can be given to anyone requiring blood
What is the universal blood type acceptor?
People with AB - can accept any blood type - they have no antibodies
How can you determine what blood type someone is?
Look at their blood for the relevant antigen
Look at their blood plasma for the antibodies that are present
What are the different rhesus blood types?
C or c
D or no D (no D is written as d)
E or e
Are antibodies produced against the rhesus blood types?
Not naturally produced - will only be produced via the immune system
Produced if someone is exposed to the antigen through transfusion, pregnancy, transplantation
What will the rhesus phenotype of CcDe be agglutinated by?
Anti-C
Anti-c
Anti-D
Anti-e
What will the rhesus phenotype cdE be agglutinated by?
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
Which rhesus antigen is the most clinically important and why?
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
What is haemolytic disease of the newborn? (HDN)
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
How is HDN prevented?
Rhesus negative mothers carrying rhesus positive babies are given prophylactic anti-D antibodies
What are the different types of blood transfusion that can be provided?
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
What are the risks of a blood transfusion?
Transmit infection Alloimmunisation - antibody production which could compromise future transfusion Incompatible transfusion Iron overload from multiple transfusions Circulatory overload
What is the purpose of the indirect antiglobulin test?
Used to screen for atypical antibodies in the patient’s plasma
