Blood Transfusions Flashcards
What does the ABO blood group system refer to?
The type of antigen present on our cells.
What antibodies are present in people with O group blood and why?
Anti-A and anti-B. They have no antigens on their blood cells and so are hostile to any blood antigen.
What type of antibody are the blood antigen detecting antibodies?
What do they cause when they come into contact with a complementary antigen?
They are IgM class and cause haemolysis.
How are A and B antigens formed?
By adding a sugar residue onto a common glycoprotein and fucose stem (known as H antigen/stem).
How are Group O’s “antigens” formed?
Group O consists of the common H stem/antigen made of glycoproteins and fucose but doesn’t have any other sugar molecule bound to it.
What does the A gene code for?
An enzyme that adds N-acetyl galactosamine to the common H antigen.
What does the B gene code for?
The 🅱️ gene codes for an enzyme that adds galactose to the common H antigen.
How are all the genes related to each other in terms of dominance?
O gene is recessive - it is simply the lack of coding of the enzyme that adds a sugar, therefore having an O and an A gene will lead to A antigens being produced.
A and B are co dominant - they will both cause their respective antigens to be produced.
Adding IgM antibodies to complementary antigens will cause what to form?
Clumps will form, this is known as agglutination.
E.g. A group B patient has anti-A antibodies which when added to group A cells will cause agglutination.
What does the Rh system refer to?
The Rh system is the Rhesus system.
The presence/absence of the D antigen.
Blood can either be RhD positive or RhD negative.
What genes are responsible for the D antigen?
D genes code for the D antigen.
d gene doesn’t code for an antigen and so is recessive.
People who lack the RhD antigen have what blood antibodies?
They will have anti-A and/or anti B antigens, or neither if their blood group is AB. They will only get anti-D antibodies once they are sensitised to the RhD antigen. Anti-D antibodies are IgG class.
Name two ways in which someone lacking a D antigen can be exposed to D antigens.
- Blood transfusion from a D positive donor.
2. A mother who is D negative being pregnant with a foetus who is D positive
What are two future implications of have anti-D antibodies?
- Future transfusion - the patient will have to have RhD negative blood otherwise they would break down the blood cells, causing delayed haemolytic transfusion reaction with anaemia, high bilirubin levels (causing jaundice), with potentially fatal consequences.
- Haemolytic Disease of the Newborn (HDN) - Will go into more depth on another flashcard.
What is HDN?
Haemolytic Disease of the Newborn (HDN).
If a mother has anti-D antibodies, the IgG antibodies will cross the placenta (the only kind of antibodies that can) and cause haemolysis of the foetus’ blood cells.
