Blood groups evaluation Flashcards
Explain the immune reaction caused by incorrect transfusion of blood
Antibodies of plasma will react with the antigens on the surface of the RBS, of another blood type.
2 types of antigens are more likely than others to cause immune reaction.
OAB system and Rh system.
Explain blood transfusion agglutination
When blood is mixed, for example type A antibodies with type A blood cells. Then the type A antibodies attach to the RBC.
IgG has 2 binding sites and IgM has 10.
The cells bind together and forms a clump –> Agglutination.
The RBC’s will then get attacked by phagocytotic WBC’s which cause haemolysis.
What is the agglutination test?
Used to test blood type.
Mix serum with type A antibodies with different blood.
Check if agglutination occurs.
Explain the Rhesus system
Difference between OAB and Rh system:
In OAB system, the agglutinins responsible for causing reaction develop spontaneously.
In Rh system, there are no spontaneous developments of antibodies.
Instead a person must be exposed to an Eh antigen that will initiate a development of Rh antibodies that will cause a reaction the next time this person is exposed.
There are 6 types of Rh antigens (called Rh factor).
C, c, E, e, D and d.
The D factor is more common and a person with this type is Rh positive, and if you lack it, you are Rh negative.
The Rh- is cased by recessive homozygous dd, while Rh+ is caused by either DD or Dd.
How are Rh- antibodies formed?
When Rh+ blood is transfused into an Rh- person then Rh- antibodies (agains Rh+) start to develop, slowly.
Reaching a maximum concentration in 2-4 months. First exposure usually doesn’t cause much response.
After 2-4 weeks anti-Rh antibodies have been produced in sufficient amount to cause a reaction with any transfused blood still circulating.
This is a delayed transfusion reaction, which is mild.
The next time, the reaction will be quicker and more severe since the person then already has anti-Rh antibodies in his/her system.
What is erythroblastosis fetalis
A disease where the newborn child suffers from agglutination.
Caused in most cases due to Rh- mother and Rh+ father (Rh+ then passed onto child).
The mother develops anti-Rh agglutinins from exposure to the fetus’ Rh antigen, and these antibodies diffuse though the placenta and agglutinates the fetus’ blood.
This does not happen with the first child, because the initial immune response is too slow. Occurs with the second child, when immune response is already fully developed.
Treatment:
Replacing the newborns Rh+ blood with Rh- blood.
This destroys the anti-Rh agglutinins from the mother.
Prevention:
Administration of anti-D antibody to the mother.
