sero m7p2

• Opsonization

  C3b and C1q enhance phagocytosis
• Chemotaxis


  C5a and C5, 6, 7, 8 complex
• C5a


  • enhance adhesiveness of neutrophils to the endothelium

  
  

  • serves as chemoattractants for chemotaxis
• Anaphylatoxin

  • Complement proteins like C5a, C3a, and C2a

  
  

  • Bind directly to smooth muscles of bronchioles bronchospasm -> bronchospasm
• Histamine


  one of the agents that induces an increase in vascular permeability
• Cytolysis (MAC)


  disrupt the membrane and entry of water and electrolytes into the cell
• Enhancement of antibody production


  binding of C3b to its receptors on the surface of activated B cells
• Regulators of C3 and C5 convertases


  • DAF (Decay accelerating factor)

  • FACTOR I

  • C4b-binding protein (C4BP)
• DAF (Decay accelerating factor)

  • Encoded by CD55G

  
  

  • Glycoprotein on surface of human cells

  
  

  • Prevents assembly of C3bBb; no formation on MAC
• DAF (Decay accelerating factor)


  • Deficient DAF - cause PNH

  
  

  • Unusual feature, acquired mutation in defective gene, in hematopoietic stem cells

  
  

  • Acts in BOTH Classical and Alternative pathway.

  
  

  • Dissociates C3 convertase
• FACTOR I

  • Plasma serine protease degrade cell-associated C3b

  
  

  • Active ONLY in presence of regulatory proteins MCP, factor H, C4BP and CR1 complement receptors that servers as CO FACTORS

  
  

  • cleaves C3b and C4b
• C4b-binding protein (C4BP)


  • Inhibits the action of C4b in the CLASSICAL PATHWAY

  
  

  • Splits C4 convertase

  
  

  • COFACTOR of FACTOR I

  
  

  • Inactivates the action of C4b
• Factor H


  • Regulates the ALTERNATIVE PATHWAY

  
  

  • Prevents binding of factor B to C3b

  
  

  • Facilitates binding of Factor I
• Factor H

  • cleaves C3b to inactive iC3b

  
  

  • cleaves C4b to inactive fragments
• S protein "Vitronectin"


  • Prevent insertion into cell membranes near the site where the complement cascade was initiated

  
  

  • Prevents attachment of the C5b67 complex to cell memb. Binding to soluble C5b,6,7
• CD 59 "Protectin"


  • Inhibits formation of MAC by binding to C5, 6, 7, 8

  
  

  • Present on normal cells where it limits MAC formation

  
  

  • NOT PRESENT ON MICROBES
• HRF (Homologous Restriction Factor)


  • Inhibits MAC formation

  
  

  • Bind to C8, Inhibits C9 binding
• Regulators of Classical and Lectin Pathway


  C1 Inhibitor (C1 INH)
• C1 Inhibitor (C1 INH)


  • inactivates C1 by dissociating C1r and C1s from C1

  
  

  • Inactivates MASP-2 in lectin pathway

  
  

  • Act in concert with Factor I to inhibit C3 convertase
• C1 Inhibitor (C1 INH)

  • C4BP

  • DAF

  • MCP

  • CR1
• Regulators of Alternative Pathway


  • Factor I

  • Factor H
• Factor I


  cleaves C3b and C4b
• Factor H

  cofactor with Factor I to inactivate C3b and prevents binding of Factor B to C3b

  
  

  Factor B = ALTERNATIVE PATHWAY
• C1q


  [CLASSICAL PATHWAY]

  Binds to Fc of IgM and IgG
• C1r


  [CLASSICAL PATHWAY]

  Activates C1s
• C1s


  [CLASSICAL PATHWAY]

  Cleaves C4 and C2
• C4


  [CLASSICAL PATHWAY]

  Part of C3 convertase
• C2


  [CLASSICAL PATHWAY]

  Binds to C4b form C3 conv
• C3


  [CLASSICAL PATHWAY]

  Key intermediate in all path
• C5


  [CLASSICAL PATHWAY]

  Initiates MAC
• C6


  [CLASSICAL PATHWAY]

  Binds to C5b in MAC
• C7


  [CLASSICAL PATHWAY]

  Binds to C5bC6 in MAC
• C8


  [CLASSICAL PATHWAY]

  Starts pore formation
• C9


  [CLASSICAL PATHWAY]

  Polymerizes to cause lysis
• Factor B


  [ALTERNATIVE PATHWAY]

  Binds C3b to form C3 conv.
• Factor D


  [ALTERNATIVE PATHWAY]

  Cleaves Factor B
• Properdin


  [ALTERNATIVE PATHWAY]

  • Stabilizes C3 convertase

  • Protects C3b