Week 15 - Blood I

Question 1

Normocytic Anemia

Question 2

MCV

Question 3

Hemoglobin

Question 4

WBC ranges

Question 5

Thrombotic Thrombotocytopenic

Question 6

Schistocytes

Question 7

Spherocytes

Question 8

Blood Groups

Answer 8

44 recognized blood groups
- 2 clinically relevant :
- ABO
- RhD

Question 9

ABO Blood Group

Answer 9

• 3 allelic forms: A, B, O
• A and B encode 2 different enzymes that add a distinct monosaccharide to carb chains on glycoproteins to create distinct RBC surface grlycoprotien antigens A and B
• O encodes inactive enzyme -> no antigen made
• immune system makes antibodies against whichever ABO blood group antigents are NOT found on the person’s RBCs
• The antibodies are naturally occuring IgM (form without exposure to ABO qaqntigens)
• these antibodies are haemolytic – activate complement and cause RBC destruction
• 6 genotypes, 4 different blood groups
  - AA or AO –> A (makes b antibodies)
  - BB or BO –> B (makes A antibodies)
  - AB –> AB (makes no antibodies, universal recipient)
  - OO –> O (activates no antibodies, universal donor)

Question 10

ABO incompatible transfusion

(how does the reaction take place?)

Answer 10

• incompatible tranfussion causes an immediate acute haemolytic transfusion reaction
  Ex:

Anti-A from recipient meets A antigen on donor RBCs–> Histamine release (flushing, hypotension, tachycardia) –> MAC attack perforates RBC membrane –> osmotoc lysis
cytokines are also released from WBC (fever and chills)

Question 11

Rh Blood Group

Answer 11

• most important antigen in the Rh system is Rh D (Rh factor)
• RBC with Rh D -> Rh +
• RBC without Rh D -> Rh -
• Rh antigens encoded at the Rh locus. Rh - means RHD gene is inactive or deleted
• no naturally occuring anti-D antibodies
• Rh D- received blood from Rh D+ –> no immediate hemolytic reaction
  
  • HOWEVER anti D antibodies will form so subsequent exposure to D+ RBCs may cause **delayed hemolytic reaction **
• O- blood is the true universal donor

Question 12

Haemolytic Disease of the Newborn

Answer 12

• aka erythroblastosis foetalis
• occurs in D+ neonates with D- mothers
• pathophysiology –> first pregnancy exposure (even small placental tear allows foetal RBC to cross into maternal circulation) —> Foetal RBc cause formation of anti-D antibodies in mother –> primary antibody response is IgM which does not cross placental barrier –> first pregnancy unaffected
• second pregnancy exposure –> even a small exposure of mother (D-) to fetus (D+) can cause a secondary antibody response (anti-D IgG) –> IgG cross placental barrier and coat fetal D+ RBC causeing hemolysis