Complement System

Question 1

what is the complement system?

Answer 1

Part of the innate immune system. Large number of plasma proteins that are activated locally at infection sites to produce an enzyme-triggered cascade of inflammatory events. Three main anti-infection methods: opsonization, recruiting/activating phagocytes, MAC.

Question 2

name the 3 complement activation pathways & their triggers

Answer 2

1) Classical: immune complexes
2) Lectin: microbial sugars
3) Alternative: microbial surfaces

Question 3

C3a: 3 roles

Answer 3

1) Mast cell (blood) degranulation
2) Basophil (tissue) degranulation
3) Neutrophil chemotaxis

Question 4

C3b: 2 roles

Answer 4

1) Opsonization

2) Clears immune complexes by linking to RBCs

Question 5

C3d: 2 roles

Answer 5

1) Opsonization

2) B cell activation

Question 6

C5a: 3 roles

Answer 6

1) Mast cell (blood) degranulation
2) Basophil (tissue) degranulation
3) Neutrophil chemotaxis

Question 7

What complement components make up the MAC?

Answer 7

C5b, 6, 7, 8, 9

Question 8

Role of the MAC

Answer 8

lyses microorganisms

Question 9

What complement components are involved in opsonization?

Answer 9

C3b , C3d

Question 10

What complement components are involved in neutrophil chemotaxis?

Answer 10

C3a , C5a

Question 11

What complement components are involved in basophil & mast cell degranulation?

Answer 11

C3a , C5a

Question 12

What is the role of the C3 convertase? Which are different with the pathway variations?

Answer 12

Splits C3 to C3a/C3b.

Classical/Lectin pathways make one type (C4b2a), Alternative makes another (C3bBb)

Question 13

What is the role of the C5 convertase? What is it formed from in the 3 pathways?

Answer 13

Splits C5 to C5a/C5b.

Classical/Lectin make one type (C4b2a3b), Alternative makes another (C3bBb3b)