Blood Groups and Transfusions

Question 1

There are >30 common and >100 are blood group Ags. They are GENERALLY found on______ and are mostly (molecule).

Answer 1

found on RBC surface
Glycoproteins

Question 2

What are agglutinins?

Answer 2

Anti-A/B Abs

Question 3

The concentration of Anti-A/B agglutinins ________ as a person ages.

Answer 3

Decreases

Question 4

On average the titre of which (Anti-A/B) agglutinins is higher than the other in respective blood groups?

Answer 4

Anti-A in B and O > Anti-B in A and O

Question 5

What are the 2 main immunogenic blood group Ags?

Answer 5

ABO and Rh

Question 6

The ABO alleles are on which chromosome?

Answer 6

chromosome 9

Question 7

A and B alleles are _______ over O alleles which are ____.

Answer 7

co-dominant
recessive

Question 8

How are A, B and O antigens produced in individuals with respective alleles?

Answer 8

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

Question 9

What is Rh group?

Answer 9

Rhesus group is a group of RBC surface transmembrane proteins

Question 10

Which Rh form is used to classify Rh+/- blood group?

Answer 10

Rh D (Most immunogenic)

Question 11

Which chromosome is the RhD gene on?

Answer 11

Chromosome 1

Question 12

When does transfusion reaction occur when a Rh- px receives Rh+ blood?

Answer 12

2-4 week after 1st exposure

Question 13

What proportion of the population is Rh-?

Answer 13

about 5%

Question 14

What happens when you introduce incompatible blood into a px?

Answer 14

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

Question 15

What are some clinical presentations of haemolytic transfusion reaction?

Answer 15

Mild:
- Fever/chills

Severe:
- Jaundice
- Renal failure
- Disseminated Intravascular Coagulation (DIC)

Question 16

How is blood group crossmatching done?

Answer 16

Donor RBC added to recipient serum to test for agglutination

Question 17

Rh+ px can donate to ______ and receive from ______.

Answer 17

donate to other Rh+
receive from either Rh+/-

Question 18

Rh- can donate to ________ and receive from ______.

Answer 18

donate to either Rh+/-
receive only from Rh-

Question 19

What is haemolytic disease of the newborn?

Answer 19

Alloimmune rxn between Rh- mother and non-1st Rh+ newborn

Question 20

What is the pathogenesis of haemolytic disease of the newborn?

Answer 20

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

Question 21

What can be used to mitigate haemolytic disease of the newborn?

Answer 21

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)

Question 22

Can ABO incompatibility cause Haemolytic Disease of the Newborn?

Answer 22

No (AB antigens not fully developed in fetus)

Question 23

What are some symptoms/complications of Haemolytic Disease of the Newborn?

Answer 23

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)