Test 1: lecture 14 classic Flashcards
C3 has a ___ that is activated by protein cleavage
thioester → will bind covalently to pathogen
3 ways classical complement pathway can be activated
C reactive protein
multivalent IgM antibody
clustered of IgG
___ will bind to C reactive protein, IgM antibody or a cluster of IgG
C1 (classical pathway)
C reactive protein binds to ___ found in bacterial and fungal lipopolysaccharides or damaged human cell membranes
phosphocholine
shape and function of c-reactive protein
pentamer that changes its formation when it binds to phosphocholine found in bacterial and fungal lipopolysaccharides or damaged human cell membranes
classical complement pathway
formation of C1
18 C1q form together
two C1r (inactive serine proteases)
two C1s (inactive serine proteases)
C1 will bind to C-reactive protein and start the classical complement pathway
classical pathway activation
IgM, cluster of IgG or c-reactive protein bind to pathogen and change shape
C1 binds and activates “lectin pathway”
C4 is cleaved by active C1 into → C4b and C4a
C4b binds to pathogen
C2 is cleaved by active C1 and will bind to pathogen bound C4b → C4bC2a (classical C3 convertase)
C4bC2a will cleave C3 → C3b and C3a
C3b bind to pathogen and can trigger effector mechanism → phagocytosis or MAC (membrane attack complex → makes holes and lysis pathogen)
C3b can lead to amplification by cleaving factor B and binding to Bb → C3bBb which is another C3 convertases
___ is the classical and lectin C3 convertase
C4bC2a
IL-1/IL-6/TNF alpha can induce acute-phase proteins to be produced by the ___ and leads to ___
liver
lectin pathway (by MBL)
classical pathway (by C reactive protein)
what is used in the alternative pathway for C3 convertases?
C3bBb
iC3Bb (soluble)
what is used in the lectin pathway for C3 convertase?
C4bC2a (same thing used by classical pathway)
what is used by classical pathway to cleave C3?
C4bC2a (same thing as lectin)
___ is used in complement during amplification
C3bCb
used by all three pathways
complement regulation
H, DAF and MCP will turn off complement
factor H and complement
C3b on host surface will recruit H
H will bind to C3b and host specific carbohydrate
will recruit Factor I
this will cleave C3b → iC3b and I and H and a piece of C3b will float off to start again
DAF and complement
DAF(decay accelerating factor)
on host cell surface
will bind to C3bBb and inactive it by kicking Bb off
MCP and complement
Membrane co-Factor protein
deactivate complement→ found on host surface
MCP will bind to C3bBb and kick off Bb
it will then recruit Factor I which will cleave C3b into → iC3b
three things that use CCP domains
CCP(complement control proteins):
DAF (decay accelerating factor)→ inactive C3bBb → C3b
MCP (membrane co-factor protein) inactive C3bBb→ iC3b
Factor H → inactive C3b → iC3b
___ are found on the host cell surface and control the complement system
DAF and MCP
clearance of immune complexes
antigens bind to antibody
if enough cluster together they can recruit C1 → classical pathway and leads to the binding of C3b to the antigen: Ab surface
this will tag the cell
RBC with CR1 (receptors) will bind to tagged cell and carry them to liver or spleen where the At:Ab can be eaten and destroyed
how do RBC work with classical pathway
antigens bind to antibody
if enough cluster together they can recruit C1 → classical pathway and leads to the binding of C3b to the antigen: Ab surface
this will tag the cell
RBC with CR1 (receptors) will bind to tagged cell and carry them to liver or spleen where the At:Ab can be eaten and destroyed
review of complement
