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Flashcards in Complement Deck (12):
1

C3b

2

C3a

3

C5a

4

C3a

5

Classical pathway

Triggered by fixation of C1 to antibody labeled antigen  (IgM or IgG on bug)

6

Alternative pathway

Triggered by microbial surface molecules. LPS, endotoxin, complex polysacharides, venom, etc. in the absence of antibody.

7

Lectin pathway

Mannose-binding lectin (in plasma) binds to carbohydrates on microbes and directly activates C1

8

C3 convertase

  • All 3 complement activation pathways lead to formation of active  C3 convertase
  • C3 convertase splits C3 into fragments C3a and C3b
  • C3a released 
  • C3b binds to previous fragments to form c5 convertase

9

Functions of the complement system

1. Inflammation

2. Opsonization and phagocytosis

Cell lysis

10

C5 convertase

  • Formed from C3b + other fragments.  
  • Cleaves C5 to release C5a and leave C5b attached to the cell surface
  • C5b binds late components (C6-9) and ultimately forming the MAC

11

MAC

Membrane attack complex

Composed of miultiple C9 molecules

C3 --> C3b --> C5 convertase 

C5 --> C5b --> binds with C6-C9

Multiple C9 ------> MAC 

12

Anaphylatoxins

C3a, C5a, C4a

complement components that stimulate histamine release from mast cells (^^^ vascular permeability, vasodilation)