High Yield Topics-Complement

Question 1

Complement is synthesized in what organ?

Answer 1

Live

Question 2

3 Types of complement activation pathways

Answer 2

1. Classic
2. Alternative
3. Lectin

Question 3

Which type of complement activation pathways is induced by IgG or IgM?

Answer 3

Classic

*STUDY AID: GM makes CLASSIC cars

Question 4

Which type of complement activation pathways is induced by microbe surface molecules?

Answer 4

Alternative

Question 5

Which type of complement activation pathways is induced by mannose or other sugar molecules on microbes?

Answer 5

Lectin

Question 6

All 3 types of complement activation pathways end up activating

Answer 6

C3 convertase

Question 7

Describe complement activation pathways from C3 convertase and beyond

Answer 7

1. All 3 types of complement activation pathways end up activating C3 convertase
2. C3 convertase converts C3 into C3a & C3b
   - C3a activates mast cell degranulation
   - C3b activates C5 convertase
   - C3b also plays a role in opsonization
3. C5 convertase converts C5 into C5a & C5b
   - C5a activates mast cell degranulation
   - C5a also plays a role in neutrophil chemotaxis
4. C5b joins C6-C9 to form MAC (membrane attack complex against encapsulated bacteria)

Question 8

What prevents complement activation against self cells (RBCs for example)?

Answer 8

1. DAF (aka. CD55)

2. MIRL (aka. CD59)

Question 9

What complement deficiency can increase risk for encapsulated bacteria and SLE?

Answer 9

Early complement Deficiency (C1-C4)

• Lack of C1-C4 –> can’t form MAC against encapsulated bacteria
• Impaired clearance of immune complexes –> SLE

Question 10

What complement deficiency can increase risk for Neisseria meningitis only?

Answer 10

Terminal complement Deficiency (C5-C9)

Question 11

What complement deficiency causes hereditary angioedema due to uninhibited kallikrein (increased bradykinin)

Answer 11

C1 esterase inhibitor deficiency

Question 12

Complement-mediated intravascular hemolysis that leads to dark urine especially at night (when mild acidosis can occur due to slowed breathing)

Answer 12

Paroxysmal Nocturnal Hemoglobinuria (PNH)

Question 13

What gene is defective in Paroxysmal Nocturnal Hemoglobinuria (PNH) leading to a mutation in DAF/MIRL which protects RBCs from MAC attack?

Answer 13

PIGA