2/10/17 GERMAN Barriers and soluble effectors II TEST #2 Flashcards
What is the first complement pathway to act?
-Alternative pathway
What is the second complement pathway to act?
-Lectin Pathway
What is the third complement pathway to act?
-Classical pathway
What complement pathway has mannose-binding lectin binds to pathogen surface?
-Lectin pathway
What complement pathway has a pathogen surface that creates a local environment conducive to complement activation?
-Alternative pathway
What complement pathway has C-reactive protein or an antibody that binds to specific antigens on pathogen surfaces?
-Classical pathway
What complement protein covalently binds to surface components of the pathogen?
-C3b
When a complement protein is cleaved what size is the “a” portions?
-Small fragment
What two things activate the classical pathway?
- C-reactive protein
- Antibodies
What complement protein initiates the classical pathway?
-C1q
What does C1q bind to?
-The conservative region of the antibody
What two types of antibodies typically activate the complement system?
- IgM
- IgG
Does IgG or IgM bind C1q with a higher affinity?
-IgM
How many IgG’s are needed for C1q to bind?
-At least 2
When C1q is bound what does it activate?
- C1r
- C1s
What does C1r2s2 cleave?
C4
What does the C4b bind to?
-C2
What is the lectin pathway initiated by?
- Mannose Binding lectins
- Ficolins
What does the lectin pathway target?
-Pathogen cell surface carbohydrates
What does the MBL and Ficolins recruit?
- MBL associated serine protease such as:
- MASP-1
- MASP-2
What is C4b2a also known as?
-C3 convertase
What is C4b2a3b also known as?
-C5 convertase
What do serine proteases cleave in complement?
-C4
In the lectin pathway what cleaves C2?
-MASP-2
What cleaves C4 in the lectin pathway?
-activated MASP-2 with MBL or Ficolin
What are the three routes of activation in the alternative pathway?
- Spontaneous C3 hydrolysis
- Properdin-pathogen binding and C3 recruitment
- Proteolytic C3 cleavage
What are two examples of proteolytic C3 cleavage?
- Thrombin
- Clotting cascade proteases
When C3 spontaneously changes conformation (gets cleaved) what does it expose?
-Thioester bond
T/F C3 thioester bond is unstable in aqueous environments
True
What are three C3 convertases?
- iC3Bb
- C3bBb
- C4b2a
What C3 convertase initiates the alternative pathway?
-iC3Bb
What C3 convertase drives pathogen C3b opsonization?
-C3bBb
What does properdin do?
-Bind to pathogen surfaces and recruits C3b
What is C3b2Bb?
-C5 convertase
T/F Small complement-cleavage products act on blood vessels to increase vascular permeability and cell-adhesion molecules
True
C3a, C5a, and C4a are known as what?
-Anaphylatoxins
What do anaphylatoxins activate?
-Innate immune cells
What does opsonization do?
-Neutralizes pathogens and targets them for phagocytosis
When only C3b binds to CR1 are bacteria phagocytosed?
-No
What can C5a activate?
-Macrophages to phagocytose via CR1
When you have C5b what does that recruit?
- C6
- C7
When you have a C5b, C6, and C7 complex what do you recruit?
-C8
When you have the C5b, C6, C7, and C8 complex what do you recruit?
-C9 to create a pore (Membrane Attack Complex)
What can bind do the C5b678 complex to prevent the C9 recruitment and pore formation?
-CD59
Removal of what is critical in preventing complement from targeting self-cells?
- C3b
- C5b
What factors lead to C3 depletion and pathogen susceptibility?
- Factor H
- I
- DAF
- MCB
What two complement proteins recruit phagocytic cells to the site of infection and promote inflammation?
- C3a
- C5a
What cleaves C4b2?
-C1r2s2 complex
