Blood Groups and Transfusions Flashcards
There are >30 common and >100 are blood group Ags. They are GENERALLY found on______ and are mostly (molecule).
found on RBC surface
Glycoproteins
What are agglutinins?
Anti-A/B Abs
The concentration of Anti-A/B agglutinins ________ as a person ages.
Decreases
On average the titre of which (Anti-A/B) agglutinins is higher than the other in respective blood groups?
Anti-A in B and O > Anti-B in A and O
What are the 2 main immunogenic blood group Ags?
ABO and Rh
The ABO alleles are on which chromosome?
chromosome 9
A and B alleles are _______ over O alleles which are ____.
co-dominant
recessive
How are A, B and O antigens produced in individuals with respective alleles?
A allele encodes for N-acetylgalactosamine (GalNAc) Transferase
- adds GalNAc to end of A antigen glycoprotein
B allele encodes for Galactose (Gal) Transferase
- adds Gal to end of B antigen glycoprotein
O allele encodesfor dysfunctional enzyme
- no carbohydrate added to end of antigen
What is Rh group?
Rhesus group is a group of RBC surface transmembrane proteins
Which Rh form is used to classify Rh+/- blood group?
Rh D (Most immunogenic)
Which chromosome is the RhD gene on?
Chromosome 1
When does transfusion reaction occur when a Rh- px receives Rh+ blood?
2-4 week after 1st exposure
What proportion of the population is Rh-?
about 5%
What happens when you introduce incompatible blood into a px?
Haemolytic transfusion reaction:
1) RBCs agglutinated by respective Abs
2) RBCs trapped and haemolysed by macrophages in spleen/liver
3) Intravascular haemolysis by complement system
What are some clinical presentations of haemolytic transfusion reaction?
Mild:
- Fever/chills
Severe:
- Jaundice
- Renal failure
- Disseminated Intravascular Coagulation (DIC)
How is blood group crossmatching done?
Donor RBC added to recipient serum to test for agglutination
Rh+ px can donate to ______ and receive from ______.
donate to other Rh+
receive from either Rh+/-
Rh- can donate to ________ and receive from ______.
donate to either Rh+/-
receive only from Rh-
What is haemolytic disease of the newborn?
Alloimmune rxn between Rh- mother and non-1st Rh+ newborn
What is the pathogenesis of haemolytic disease of the newborn?
1) Exposure of mother to Rh+ RBC during 1st labour sensitises mother to RhD Ags
2) Anti-D IgG develop between pregnancies
3) During 2nd pregnancy, anti-D IgG cross placental barrier to attack RBC of fetus
What can be used to mitigate haemolytic disease of the newborn?
Anti-D injection at 3rd trimester (28 weeks) of 1st pregnancy
- Rh+ RBC entering maternal circulation rapidly bound and cleared before stimulating maternal adaptive immunity
(prevent sensitisation)
Can ABO incompatibility cause Haemolytic Disease of the Newborn?
No (AB antigens not fully developed in fetus)
What are some symptoms/complications of Haemolytic Disease of the Newborn?
1) Haemolytic anemia
2) Jaundice
3) Hepatosplenomegaly
4) Erythroblasts in circulation (compensatory but immature)
5) Neurotoxicity (toxic bilirubin conc. + underdeveloped BBB in fetus)
6) Severe oedema/hydrops fetalis (change in osmotic pressure by unconjugated bilirubin)
