Session 13: Intro to red blood cells and hemostasis

Question 1

How many blood group systems exist?

Answer 1

36

Question 2

Name the 2 most important types of blood group systems.

Answer 2

• ABO system

- Rh system

Question 3

Discuss the characteristics of the antibodies of the ABO blood system.

Answer 3

• Naturally occurring
• AKA isohaemagglutinins
• Produced w/o immunisation stimulus
• Not present @ birth
• Develop @ +/- 3-6 months of age
• Produced in response to antigens in
  bacteria, viruses, etc.
• Don’t react w/ antigens from same group
• Usually IgM (cannot cross placenta)

Question 4

Describe the Rh blood system.

Answer 4

• Factor D most common
  and potent antigen
• If D antigen present = Rh +
• If D antigen is absent = Rh

Question 5

Discuss the characteristics of the antibodies of the Rh blood system.

Answer 5

• Immune antibodies
• Allo-antibodies (not
  naturally occurring)
• Only occur after previous
  sensitisation, e.g
• blood transfusion between
  Rh+ and Rh- individuals
• presence of Rh+ foetus in
  a Rh- mother
• IgG (can cross placenta)
• causes HDFN

Question 6

Discuss HDFN (haemolytic disease of the foetus and newborn)/ erythroblastosis fetalis in detail.

Answer 6

- Commonly caused by anti-D 
  antibodies 
- Rh- mother sensitised to 
  Rh+ RBCs via previous 
  pregnancy of blood 
  transfusion w/ Rh+ blood
- Mom's immune system 
  recognises D-antigen as 
  foreign and develops IgG 
  antibodies against it 
- W/ next pregnancy, anti 
  D-antibodies cross 
  placenta, enter foetal 
  circulation
- Binds the foetal RBCs and 
  haemolyse it

Question 7

Name and describe the effects of the three clinical syndromes due to haemolytic disease of the foetus and newborn (HDFN).

Answer 7

1. Hydrops fetalis- foetus is
   oedematus and dies in
   utero/ shortly after birth
2. Icterus gravis neonatorum - severe jaundice and
   anaemia in newborn
3. Kernicterus: brain damage
   due to severe
   hyperbulirubinaemia

Question 8

What happens in compatible blood transfusions?

Answer 8

• Recipient receives blood
  of the same ABO and
  Rh group.

Question 9

What happens in incompatible blood transfusions?

Answer 9

• Recipient receives blood
  of different ABO and Rh
  blood group.
• Antibodies in the plasma
  of recipient react w/
  antigens on RBCs of
  donor.
• Donor’s RBC are
  haemolysed

Question 10

What is the purpose of compatibility testing/cross matching?

Answer 10

- Ensures that the 
  transfused blood will 
  survive in the recipient's 
  system and be of benefit 
  to the patient

• Checks whether
  recipient’s serum contains
  antibodies to the donor’s
  red cell antigens.