Lecture 3 - Complement Flashcards
What is complement
augmented opsonization working with the actions of antibodies
What 3 pathways make up the complement system?
1 - classical
2 - alternative
3 - lectin
What component of blood is the complement system found
plasma
T/F: the complement system is part of the adaptive defense system
False - innate
T/F: the complement system plays a regulatory role in the adaptive immune system
True
T/F: complements do not need to be activated as they are a natural part of the immune system
False - they must be activated via a cascade pathway
What are the biochemical principles of complement systems
- synthesized as inactive precursors
- activated via cleavage
- results in active complement protease
- amplification
what is added to an inactive complements name once it is cleaved
a lowercase suffix
What is a complex of complements called
a factor
what activates the complement system
- pathogen itself
- antibody bound to pathogen
T/F: all pathways create a common effector complement protein
True
what are the effector proteins created by complement pathways
C3a, C3b, C5b, MAC, C3 convertase
What is the final goal of the three complement pathways
removal of the pathogen
The classical pathway is activated by:
antibody bound to the pathogen
The MBL (mannose-binding lectin) pathway is activated by:
lectin binds to mannose on the pathogen cell wall
The alternative pathway is activated by:
binding of a complement directly to the pathogen surface
Summarize the classical pathway in 5 steps
1 - C1 binds to antibody
2 - conformational changes cleave C4 and C2 proteins
3 - C4b and C2b combine (C3 convertase)
4 - C3 is cleaved
5 - C3b binds and activates C5 which stimulates MAC formation
Summarize the alternative pathway in 5 steps
1 - spontaneous breakdown of C3
2 - if C3b binds to a healthy cell, factors H and I cause C3b degradation
3 - if C3b binds to a pathogen, factor H and I do not bind
4 - C3b will bind factor B
5 - B is cleaved by factor D which creates an alternate C3 convertase
Summarize the MBL pathway in 5 steps
1 - lectin complex binds to lectin
2 - MASP cleaves C4 and C2
3 - C4b and C2b combine (C3 convertase)
4 - combined complex cleaves C3
5 - C3b binds and activates C5 which stimulates MAC formation
Which pathway requires the adaptive immune system to initiate?
Classical
Which pathway uses factors and letters instead of numbers?
alternative
What does C3 convertase cause
- recruitment of inflammatory cells
- opsonization
- lysis of cell membrane
Which complement component is an anaphylatoxin
C3a
Which complement component is an opsonin
C3b
