Innate Immunity Flashcards
Where are complement proteins made? How many are there?
Liver - 20
What molecule binds to the surface of bacteria in all pathways of complement system? What can this molecule be cleaved to in order to opsonize invaders and tag them for phagocytosis by macrophages?
C3b
iC3b - opsonization/phagocytosis
What attack complex forms and lyses microbes in the complement system?
MAC
Why aren’t human cells attacked by MAC complexes? (2 reasons)
- MCP on surface of human cells clips C3b to inactive form
2. DAF - decay accelerating factor accelerates destruction of C3 convertase (C3bBb)
What protein cleaves C3 to make C3b?
C3bBb aka C3 convertase
What protein forms from the binding of C3b and C3 convertase?
C3bBb3b (C5 convertase)
What does C5 convertase do?
Cleaves C5 to make C5b
What complement proteins combine to form the MAC (membrane attack complex)?
C5b, C6, C7, C8, C9
What is the name of the pathway that acts spontaneously and on microbial surfaces to form the MAC complex?
Alternative pathway
What is the name of the pathway that makes C3b non-spontaneously to form the MAC complex?
Lectin pathway
Besides C3bBb, what is another C3 convertase (used in lectin and classical pathways)?
C4b2a
What molecule does the lectin pathway use to bind to MASP and make C4b?
MBL (mannose-binding lectin)
What is the name of the pathway that is antibody dependent to form MAC?
Classical pathway
What are the three stages of readiness for macrophages?
- Resting state - scavengers
- Primed state - barriers have been penetrated
- Hyperactivated/killing state - attain direct signals from invader
What cytokine do neutrophils produce to draw other immune cells?
TNF
What molecules are present on endothelial cells that allow neutrophils to bind? What molecules are present on the neutrophils to allow them to bind?
Endothelial cells - ICAMs and selectins (SEL)
Neutrophils - integrins, selectin ligand (SLIG)
What bacterial protein and complement protein trigger neutrophil expression of integrins?
C5a and LPS
How do natural killer cells destroy cells? What types of receptors do NK cells recognize and thus allow to survive?
Inject granzyme B into target cell, which stimulates caspases and interact with Fas on surface of target cell–> induce apoptosis
NK cells recognize MHC-I
What molecule and cytokines activates NK cells for killing?
LPS (on bacterial cell walls)
IFN-a, IFN-b (given off by cells when attacked by viruses)
What cytokine do NK cells release when activated? What does this stimulate?
IFN-gamma
Stimulates macrophages to make TNF and IL-12
What cytokine, made by NK cells themselves, as well as by macrophages, tells the NK cells to proliferate?
IL-2
