Blood group and transfusion

Question 1

Types of blood transfusion

Answer 1

Packed RBC

WBC

Platelets

Frozen plasma

Question 2

How is frozen plasma stored after it’s thawed?

Answer 2

Cryoprecipitates

Question 3

What is an antigen?

Answer 3

Substances foreign to the immune system
- Ab generator

Question 4

What is an Ab?

Answer 4

Y-shaped protein that recognises specific antigen

Question 5

Why is transfusion rxn an immune response?

Answer 5

Surface antigens on RBCs stimulate immune rxn

Question 6

What is blood grp antigens made of?

Answer 6

Glycoproteins

Question 7

Where are ABO antigens coded?

Answer 7

Allele of chromosome 9

Question 8

How is A antigen coded for?

Answer 8

A allele code for GalNAc transferase -> transferred to surface of RBC -> A antigen

Question 9

How is B antigen coded for?

Answer 9

B allele code for Gal transferase -> transferred to surface of RBC -> B antigen

Question 10

How is O antigen formed?

Answer 10

O allele code for dysfunctional enzyme -> glucose moiety not transferred -> absent glucose moiety on RBC surface results in O antigen

Question 11

What Ab are coded for after person’s blood type is determined?

Answer 11

Body will code for Ab against antigen that is not present on RBC

Question 12

What happens when there is a mismatched transfusion?

Answer 12

Recipient’s Ab binds and agglutinates donor’s RBC -> blood clumps up -> can’t squeeze through parts of capillary -> trapped in liver/spleen -> haemolytic transfusion rxn

Question 13

What is haemolytic transfusion rxn?

Answer 13

Trapped RBCs are haemolysed by macrophages in spleen/liver -> RBCs burst

Intravascular haemolysis by complement system

Question 14

Symptoms of haemolytic transfusion rxn (mild)

Answer 14

Fever/chills

Question 15

Symptoms of haemolytic transfusion rxn (severe)

Answer 15

Jaundice, renal failure, disseminated intravascular coagulation (DIC)

Question 16

Can donor’s agglutinin cause rxns?

Answer 16

Generally no

Exceptions:

Plasma transfused in low amts -> amt of foreign body introduced is so low it’s diluted.

For agglutination to happen -> need a lot of Ab to clump all the RBC tgt at a significant scale

Question 17

Is ABO the only blood antigen?

Answer 17

No

Question 18

Why is cross matching needed?

Answer 18

To screen for other reactive Ab

Question 19

How is cross matching done?

Answer 19

Cross match recipient’s serum w/ donor’s RBC -> screen for agglutination

Question 20

How is cross matching results interpreted?

Answer 20

RBC not clumping -> low risk of transfusion rxn

RBC clumps -> fatal

Question 21

Name another blood group

Answer 21

Rhesus (Rh)

Question 22

What are Rh antigens?

Answer 22

Transmembrane proteins on RBC surface

Question 23

Which Rh antigen is the most immunogenic?

Answer 23

Rh D

Question 24

What does Rh+ mean?

Answer 24

Rh D present

Question 25

What does Rh- mean?

Answer 25

Rh D absent

Question 26

How does delayed transfusion rxn happen?

Answer 26

When Rh- recipient receives Rh+ blood, anti-D Ab develops 2-4 weeks aft first exposure

Question 27

What is hemolytic disease of the newborn (HDN)?

Answer 27

Autoimmune condition involving Rh- mother and 2nd/3rd Rh+ newborn

Question 28

How is hemolytic disease of the newborn developed?

Answer 28

Exposure of mother to Rh+ RBC during 1st labour sensitizes mother to Rh D antigen -> 1st exposure is the 1st labour - placenta breaks and exposes mum to Rh+ Anti-D IgG develops in btw pregnancy - can cross placenta barrier Anti-D IgG crosses placenta to attack RBC of foetus (during 2nd pregnancy)

Question 29

Possible symptoms/ complications of HDN and how they come abt

Answer 29

Haemolytic anemia Jaundice - RBC lyse -> bilirubin released Spleno/hepatomegaly - RBC lyse -> spleen and liver work more to produce more RBC Erythroblastosis - erythroblast (premature RBC) seen in blood -> indicate sever anemia Brain damage (kernicterus) - accumulation of a lot of unconjugated bilirubin -> toxic to organ Severe edema - unconjugated bilirubin change osmotic pressure -> fluid build up Hydrops fetalis - fetus drops out - severe - fetus drops out as a result of symptoms above

Question 30

How is HDN prevented?

Answer 30

Rh grp of newborn found in 3rd trimester, anti-D injection given at 3rd trimester if have mismatch

Question 31

Why does the anti-D injection not affect the fetus in the case of HDN?

Answer 31

Dose used won't significantly impact fetus but can wipe out RBC being exposed to mum from fetus -> mom not sensitised

Question 32

How does anti-D injection prevent HDN?

Answer 32

Rh+ RBC that entered maternal circulation rapidly bound and cleared before immune system is stimulated -> fetus unaffected

Question 33

Can ABO incompatibility cause HDN and why?

Answer 33

No ABO not fully developed during pregnancy -> Ab from mom won't attack as antigen on baby's not even formed yet

Question 34

What does anti-A mean?

Answer 34

It binds to A antigen