Blood groups Flashcards
What type of molecules are antigens?
Glycoproteins
What blood group systems are used to describe a persons blood group?
ABO and presence or absence of Rhesus
What enzyme does the O genotype activate and what does this cause?
Does not activate glycosytransferase so the glycoprotein H is unmodified
What enzyme does the A genotype activate and what does this cause?
Activates A glycosytransferase so glycoprotein H is modified by antigen A
What enzyme does the B genotype activate and what does this cause?
Activates B glycosytransferase so glycoprotein H is modified with antigen B
Describe the dominance pattern of ABO
A is dominant over O
B is dominant over O
A and B are codominant
Which blood group is the universal donor and why?
O because there are no modified antigens on the surface so no agglutination will occur with any other antigen
Which blood group os the universal receivers and why?
AB - contain both of the types of modified antigen, so no immune response will be mounted as neither A B nor O will be regarded as foreign
When does agglutination occur?
When blood from incompatible blood groups are mixed e.g. A and B
Which Rhesus antigen is the most antigenic?
D
What percentage of Caucasians are Rh+ve?
85%
When does heamolytic disease of new borns occur?
During the second pregnancy of a mother that is Rh-ve having a child that is Rh+ve
If a mother is Rh-ve why is it likely that the child may get haemolytic disease?
Majority of Caucasians are Rh+ve so likelihood is the child will be
Describe how haemolytic disease of a new born manifests?
Mother (Rh-ve) carries a child (Rh+ve)
Mother will mount an immune response against the childs antibodies.
In the first pregnancy this is not harmful (primary response)
Second pregnancy = secondary immune response = haemolytic disease
Why is haemolytic disease not a concern in first pregnancies?
Only a primary immune response will be mounted
How is haemolytic disease prevented?
All mother s that are Rh-ve are given antibodies against the Rh+ve antigen which stops the antigen on the foetus being recognised as it is masked
Why are blood transfusion for patients that have had repeated transfusions harder to match?
Transfusions are first matched for Rhesus and ABO but a patient that has repeated transfusions develops immunity to other blood group antigens
