Blood Groups and Transfusion Flashcards
What are some examples of red cell antigens
ABO, Rhesus (which are the most important) and then Kell, Duffy, Kidd, MNS which are less likely to cause clinical issues
Describe the mechanism of immune haemolysis for IgM
These can be pentameric so have many binding sites that can bind to many cells. They then cause the breakdown of RBC’s rapidly in the circulation
Describe the mechanism of immune haemolysis for IgG
These antibodies bind to individual cells and then circulate into the liver and spleen where they are recognised by macrophages which can then destroy the cell.
What genes code for the H substance and what chromosome are these found on?
FUT1 and FUT2 genes which are found on chromosome 19
What genes code for glucosyl transferases, what chromosome are these on and what is the function of these?
A and B genes found on chromosome 9. The function of glucosyl transferases is to bind to the H substance adding another sugar to the chain, this determines whether the blood is A, B or O
What sugars make the blood type B or A
B - Galactose
A - N -acetlygalactosamine
For each blood group what are the RBC surface antigens and the naturally occurring antibodies
Group O no antigens and anti-A and anti-B antibodies. Group A has A antigens and Anti-B antibodies. Group B has B antigens and Anti-A antibodies. Group AB has both A and B antigens so doesn’t produce any antibodies
What is the Rhesus system?
They are another group of antigens on the surface of the RBC consisting of c, C, D, e, E. People will inherit a triplet of these antigens, eg, cDe
What does it mean to be Rhesus positive or Rhesus negative
This refers to the D antigen which is the most common. So if you have the D antigen then you are Rhesus positive and if you don’t have the D antigen then you are Rhesus negative.
Describe the haemolytic disease of the newborn
Foetal red cells carry antigens from the father that the mum does not have, these cells transfer to the mothers circulation and so the mother produced IgG antibodies against the antigen on foetal RBC’s. The antibodies cross the placenta and cause anaemia, jaundice, brain damage or foetal death.
Describe the prevention of rhesus D immunisation (HDN)
Anti-D prophylaxis is given to D negative mothers at 28 weeks and delivery and after obstetric events.
What test looks for foetal cells in the mothers circulation?
Kleihauer test
Describe some methods of foetal monitoring
This is where the mother is monitored for the development antibodies. You can monitor the baby via ultrasound by looking at flow in middle cerebral artery (in anaemic then flow rate will increase), looking for ascites (free fluid in abdo) and also looking at liver and spleen size. Can also do umbilical cord sampling
What can umbilical cord sampling tell you
Blood count, blood group and antibody level
What is the neonatal management of HDN
Clinical assesment, blood tests (reticulocytes, group, RBC antibodies and bilirubin), Coombes test, allow the antibodies to decline, phototherapy to increase bilirubin conjugation and top up transfusion or exchange transfusion.
