Flashcards in Complement Deck (85)
What are the main effector functions in complements role in killing of microbes?
opsonisation; leukocyte activation and cell lysis
What complement factor is involved in the activation of leukocytes?
What are the functions of complement?
killing of microbes; briding innate and adaptive immunity; immune complex processing; removal of apoptotic cells
What are the functions of C5a?
potent anaphylatoxin; chemotaxis; endothelial activation; prothormbotic
What are the functions of C5b-9?
cell lysis; platelet activation; endothelial activation; prothrombotic
How is the classical pathway of complement activated?
by binding of C1q to Fc portions of IgG and IgM or recognises microbial surface directly
How is the lectin pathway of complement activated?
mannose binding lectin and ficolins interacting with bacterial carbohydrate residues
How is the alternative pathway of complement activated?
What is a zymogen?
inactive pro-enzyme which become activated after proteolytic cleavage
What associates with MBL and ficolins to trigger cleavage of complement?
MBL-associated serine proteases (MASPs)
What is C1 comprised of?
recognition protein C1q assocated with proteases C1s and C1s
What do all 3 complement pathways generate?
What is C3 convertase?
a multisubunit protein with protease activity that cleaves complement component 3 (different types depending by pathway)
what is the main effector molecules of the complemetn system?
Where does C3 convertase cleave C3?
when it is bound covalently to the pathogen surface releasing C3a while leaving lots of C3b bound to the surface
What is the function of C3a?
binds to specific receptors and helps induce inflammation
What is C3b degraded into?
C3f and C3dg
How does covalent bond formation between C3b and the pathogen surface take palce?
due to highly reactive thioester bond hidden inside the folded C3 protein
What are the components of C3 convertase in the lectin and classical pathways?
What are the compoents of C3 convertase in the alternative pathway?
What is the difference in glycans between yeast and vetebrates?
yeast glycans terminate in mannose resudes rather than sialic acid residues
Where is MBL synthesised?
What is a collectin?
protein that has an amino-terminal collagen-like domain and a carboxy-terminal C-type lectin domain
What is the difference in structure between ficolins and MBL?
ficolins have a fibrinogen-like domain rather than lectin domain
How many types of ficolin do humans have?
L-ficolin (2); M-ficolin (1) and H-ficolin (3)
Where are the ficolins produced?
L and M ficolins are produced by the liver; M-ficolin is procued by lung and blood cells
What happens when MBL bound to MASP 1,2 and 3 binds to a pathogen surface?
MASP-1 is conformationally changed and activates MASP-2 which can cleave C4 and C2
What happens to C4 once activated by MASP-2?
similarly to C3, C4b has a reactive thioester which binds to pathogen surface
What happens to C2 once activated by MASP-2?
C2a remains bound to C4b