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Complement System - Coggle Diagram
Complement System
Classical Pathway
Triggers:
IgM or IgG on antigen => C1 Complex
-C1q binds Fc
-C1r, C1s activated
C4/C2 Cleavage:
C1s cleaves C4 and C2 => C4b2a assembled
C3 Convertase:
C4b2a
Cleaves C3 into C3a and C3b
C5 Convertase:
C4b2a + C3b => C4b2a3b
Cleaves C5 into C5a and C5b
C3a and C5a Anaphylatoxins
Alternative Pathway
Triggers:
C3 thiol group cleaved => C3b on cell surface
Assembly:
C3b + Factor B => C3bB
Factor D cleavage => C3bBb
C3 Convertase:
C3bBb
Cleaves C3 into C3a and C3b
Regulators:
Factor H binds C3b, competes with factor B, and displaces Bb
Factor I with MCP/CR1/C4BP cleaves C4b => C4c + C4d
Factor I with H/CR1/MCP cleaves C3b => iC3b => C3c +C3d
Both reduce C3/C5 convertases and protect host cells
C5 Convertase:
C3bBb + C3b => C3bBb3b
Cleaves C5 into C5a and C5b
Terminal Pathway, MAC formation:
C6 binds to C5b
C7 binds to C5b and C6 => C5b67, C7 penetrates membrane
C8 binds to C5b67 penetrating membrane deeper
C5b-C8 receives C9
C9 + C9 => poly-C9 transmembrane channel
C5b-C9 MAC
C3b and iC3b Opsonins
MB Lectin Pathway
Triggers:
MBL and ficolin bind to microbial sugars => MASP 1 and 2 active
C4/C2 Cleavage:
MASP-2 cleaves C4 and C2 => C4b2a assembled
C3 Convertase:
C4b2a
Cleaves C3 into C3a and C3b
C5 Convertase:
C4b2a + C3b => C4b2a3b
Cleaves C5 into C5a and C5b