4: Complement System Flashcards
In what 3 ways does the complement system eliminate bacteria?
- promotes a localized inflammatory response
- assists immune cells in phagocytosis
- damages bacterial cell membrane
3 pathways of the complement system
- classical
- MBLectin
- alternative
What enzyme do all the complement pathways converge at?
C3 convertase
3 proteins used in classical pathway
C1, C4, C2
3 proteins used in MBLectin pathways
MASP, C4, C2
3 proteins used in alternative pathway
C3b, factor B, factor D
What are C3a and C5a known as?
anaphylatoxins
What binds to create C5 convertase?
C3 convertase and C3b
Are the proteins in the complement system soluble or insoluble?
soluble
Where are the complement proteins synthesized?
liver
How is the classical pathway activated?
IgG or IgM antibodies binding to surface
How is the alternative pathway activated?
spontaneous activation in the blood or bacterial surfaces
How is the lectin pathway activated?
opsonins binding to bacterial cell surface
Which 2 proteins are the points of amplification?
C3 and C5
MBL
mannose binding lectin binds to mannose residues and other sugars on pathogens
What are the 2 serum proteins that can bind to bacterial surfaces to initiate the lectin pathway?
MBL and ficolins
Ficolins
binds to carbohydrate structures on bacterial and fungal cells to activate the lectin pathway
What is the C3 convertase in the alternative pathway?
C3bBb
What is the C3 convertase in the classical and lectin pathways?
C4b2a
What does C5b initiate formation of?
the membrane attack complex
What is the outcome of the membrane attack complex?
lysis of the cell
What type of bacteria is more resistant to the membrane attack complex?
gram-positive
Opsonization
a process which uses host proteins to tag particles such as bacteria for elimination by phagocytes
What are the 3 main complement receptors?
CR1, CR3, CR4
