IS Complement System Flashcards
series of more than 30 soluble and cell bound proteins that enhances host defense mechanisms against foreign cells
Complement
coined the term complement
Paul Ehrlich
elucidated the nature of complement
Jules Bordet
promote opsonization and lysis of foreign cells and immune complexes
Complement
may lead to inflammation and tissue damage
Chronic Activation
9 protein that are triggered by antigen- antibody combination
Classical Pathway
triggered by the binding of complement protein C1q to antibodies that are bound to pathogens or other foreign particles
Classical Pathway
main antibody directed mechanism for triggering complement activation, can only be activated by?
IgM,IgG1,IgG2, IgG3
why is IgM most efficient?
Multiple binding site
synthesized by the liver in exception with C1 components
Complement Proteins
recognition unit
C1
activation unit
C4, C2, C3
membrane attack complex
C5-C9
binds to Fc region of IgM and IgG
C1q
2 adjacent antibody molecules that recognizes the Fc region
IgG CH2 and IgM CH3
activates C1s
C1r
cleaves C4 and C2 and once activated recognition stage ends
C1s
C1q, C1r, C1s are stabilized by?
Calcium
C1r and C1s are both?
Serine protease proenzyme (Zymogen)
production of C5 convertase
Activation unit (C4, C2, C3)
cleaves complement protein C3 into C3a and C3b
C3 convertase
anaphylatoxin that causes release of histamine and attracts leukocytes to the site of inflammation
C3a
key role in formation of the membrane attack complex
C3b
C3b plays a key role in formation of the membrane attack complex which can lead to?
Lysis of target cells
proteins that forms a pore on the surface of target cells, leading to their lysis (destruction)
Membrane Attack Complex (MAC)
MAC is initiated by the activation of the complement system, which leads to?
Cleavage of C5 into C5a and C5b
? binds to C6, C7, C8, and multiple C9 molecules to form the MAC
C5b
end product of alternative pathway?
C3bBb
pathogens can be destroyed in the absence of antibodies by means of?
Alternative Pathway
represents another means of activating complement without antibody being present
Lectin Pathway
binds to mannose or related sugars in a calcium dependent manner to initiate this pathway
Mannose Binding Lectin (MBL)
considered an acute phase protein because it is produced by the liver and is normally present in serum but increases during initial inflammatory response
Mannose Binding Lectin (MBL)
dissociates C1r and C1s from C1q
C1 Inhibitor (C1INH)
cleaves c3b and c4b
Factor I
principal soluble regulator of alternative pathway; binds to C3b, preventing the binding of factor B
Factor H
acts as a cofactor with factor I to inactivate c4b (C4bp)
C4 Binding Protein
prevents attachment of C5b67 complex to cell membranes
S Protein (Vitronectin)
