Blood groups Flashcards
How are the blood group antigens determined?
They are autosomal and co-dominant - express both products
What are the differences between the protein and glycolipid determinants of blood group antigens?
Protein gene directly codes and glycolipid gene encodes enzymes that add or remove carbohydrates or lipids from the cells - ABO
What does the Duffy blood group allow?
Malaria infection.
How do naturally occurring antibodies develop?
They develop in the absence of exposure to the red cell antigen.
Most likely stimulated by cross-reacting antigens derived from bacteria.
Not present at birth but develop within 1 year.
IgM but also some IgG.
These are usual glycolipids and initiate complement. Abs are intravascular
ABO
How do immune stimulated red cell antibodies develop?
In response to red cell antigen exposure - IgG
Usually glycoproteins, not complement or only early, extravascular
RhD
What would administering the wrong blood groups cause?
Intravascular haemolysis,
Renal failure
Disseminated intravascular coagulation
What happens when you transfer RhD +ve blood cells into an RhD -ve person?
They form anti-D antibodies, which are IgG.
Extravascular destruction of RBCs
Causes haemolytic disease of the new borne
What are some of the mminor blood group antigens?
Kell
Kidd
Duffy
Why don’t IgG antibodies cause direct agglutination of RBCs?
Because the negatively charged RBCs (zeta potential) repells other RBCs and the IgG molecules are too small to over come the zeta potential. IgM is big enough.
For the IgG agglutination, use a secondary anti-human antibody to cross-link the antibodies to cause agglutination.
What is haemolytic disease of the newborn?
Maternal IgG antibodies cross the placenta and kill foetal RBCs. Most frequently is anti-D.
Causes anaemia by killing RBCs. Pre-birth, the placenta is effective at removing dead RBCs. But if the baby is born alive then the antibodies continue to kill RBCs but the baby cant clear the dead RBCs. -> jaundice. Bilirubin can cross the blood brain barrier in infants causing inflammation and kernicterus resulting in multiple neuroabnormalities.
Why does haemolytic disease of the newborn rarely impact the first child?
Because the antibody production is insufficient to cause damage.
Memory response with second child is lethal.
How do you treat haemolytic disease of the newborn?
Give anti-D to prevent primary immunisation by coating the fetal cells in the circulation.
Give following birth and during pregnancy if chance of sensitising event, e.g. abortion, amniosentesis.
Is ABO haemolytic disease a risk?
Only very slight. IgM antibodies won’t cross placenta. ABO is also weakly expressed in infants. ABO is widely expressed in placenta and will mob up AB,
What are some tests performed on donated blood?
ABO RhD HBSAg and PCR HEp C Ab and PCR HIV Ab and PCR Serology for syphilis
What happens to a blood donation?
White blood cells are removed - cause adverse effects and no benefit.
Compatibility testing.
Centrifuge to remove the plasma rich in platelets (platelet concentrate).
Centrifuge further to remove platelets from the serum (fresh frozen plasma). Some serum goes with the RBC to reducy how sticky they are (resuspended RBCs).
