The Complement System

innate defense functions

trigger inflammation

attract phagocytes

opsonize antigens

cause cell lysis

activate naïve B-lymphocytes

remove immune complexes

the classical pathway

antibody-dependent

proteins of the classical pathway

C1

6 molecules of C1q

2 molecules of C1r

2 molecules of C1s

C3

C5

Ag-Ab complex activates C1

animation showing the assembly of C1 during the classical pathway

animation showing the assembly of C3 convertase

animation showing the cleavage of C3 and the formation of C5 convertase

opsonization and phagocytosis  [C3b]

CR1 receptors

inflammation  [C5a]

the MAC and lysis  [C5b6789_n]

animation showing the formation of the MAC

agglutination

Type III hypersensitivity reaction

rheumatoid arthritis
subacute bacterial endocarditis
immune complex glomerulonephritis
systemic lupus erythematosus
Arthus reaction
Farmer’s lung
polyarteritis nodosa

viral neutralization

chemotaxis  [C5a]

animation showing the benefits of C5a and C3b

basophil/mast cell activation  [C3a, C4a, C5a]

the lectin pathway

mannan-binding lectin (MBL)–dependent

proteins of the lectin pathway

MASP1

MASP2

C4 & C2 cleaved

animation of the lectin pathway

the alternative pathway

animation of the alternative pathway and formation of C3 convertase

antibody-independent

proteins of the alternative pathway

C3

C3b

C3i

B

D

H

I

P (properdin)

animation of the formation of C5 convertase.

large polysaccharides react with factors B and D

C3bB

C3bBb

formation of activation product that activates C3

Bb

C3bBbP

regulation of complement activity

factor H

factor I

C1 inhibitor (C1INH)

complement receptors

CR1

CR2

CR3

CR4

disorders of the complement system

C3 deficiency

C2 deficiency

immune complex disorders

systemic lupus erythematosus (SLE)

C9 deficiency

C1INH deficiency

hereditary angioneurotic edema (HANE)

decay accelerating factor (DAF) deficiency

paroxysmal nocturnal hemoglobinura (PNH)

Go to beginning

Links

• Sundry sites
  • Donald Forsdyke’s comments on Intracellular Self/Not-Self Discrimination
    
    
  • M. Browning’s discussion of the Role of CD4-positive T cells in Bacterial Killing
    
    
  • Evolution of the lectin-complement pathway
    
    
  • Description of the genetics of diabetes
    
    
  • Microbial complement-targeting proteins
    
    
  • Complement quiz cards from Kuby Immunology, 4/e, by Richard A. Goldsby, Thomas J. Kindt, & Barbara A. Osborne
    
    

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[ Anatomy & Physiology 1 syllabus ] [ Page created 2008-09-11 ] [ Questions about this lecture? E-mail me ]

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