5 – Innate Immunity II

Question 1

what is th Complement system

Answer 1

Group of soluble proteins that cooperate with both innate & adaptive immune systems
To eliminate: Pathogens, Dying cells, Immune complexes from the body

Question 2

Complement systems are mostly:

Answer 2

-Mostly Proteases in blood/other fluids
Protease: enzyme that performs proteolysis – break down proteins

Question 3

most complement are called:

Answer 3

C follow by number

Question 4

other compliement are called

Answer 4

factor follow by capital letter

Question 5

Complement proteins are mostly produced by

Answer 5

Liver

Question 6

complement proteins creates a cascade, what is this?

Answer 6

Set off a chain reaction – help to clear pathogen

Question 7

key mechanisms of action (3)

Answer 7

-Increase vascular permeability (vasodilate) & chemotaxis (inflammation)
-Destroy pathogen cell membranes (poke holes)
-Increase recognition of pathogen & facilitate phagocytosis – opsonization

Question 8

what is Opsonization

Answer 8

-coating of surface of a pathogen by antibody and/or complement that makes it more easily ingested by phagocytes
-To make pathogen tastier for phagocytes

Question 9

what is phagocytosis

Answer 9

internalization of matter by cells by engulfment, in which cell membrane surrounds the material – form an intracellular vesicle (phagosome) containing ingested material

Question 10

what are inactive complements called and what do they do

Answer 10

inactive pro-proteases
-they circulate and have nothing to do

Question 11

activated in which 3 pathways

Answer 11

-classical
-lectin
-alternative

Question 12

pathway lead to a cascade of effect: what happens in this cascade?

Answer 12

all 3 pathways generate C3 convertase (cleave C3 -> C3a +C3b)

Proteolytic cleavage generates 2 fragments

Question 13

proteolytic cleavage generates 2 active fragments they are:

Answer 13

-1 small
Letter “a” after name
C5a
With specific function
-1 large
Letter “b” after name
C5b
With proteolytic activity on new substrate

Question 14

Complement nomenclature: C4b binds with C2a

Answer 14

C4b2a

Question 15

Complement nomenclature: C3b binds with Bb (factor)

Answer 15

C3bBb

Question 16

C4b2a and C3bBb are known as:

Answer 16

C3 converts

Question 17

what does C3 convertase do?

Answer 17

(cleave C3 -> C3a +C3b)

Question 18

complement proteins are only active when

Answer 18

when they are cleaved with protease

Question 19

All 3 pathways generate

Answer 19

C3 converts

Question 20

what are he 3 main outcomes from activation of pathways

Answer 20

-Inflammation
-opsonization
-MAC formation

Question 21

Lectin pathway is Triggered by: give 2 examples

Answer 21

-soluble proteins – lectins (PRR that circulate in blood)
-Not membrane-bound PRRs
Mannose-binding lectin (MBL)
Ficolin

Question 22

during infection, lectin:

Answer 22

Expression of lectin = increas

Question 23

Lectin PRRs can:

Answer 23

-PRRs can bind the surface of pathogens
-Trigger signaling cascade on pathogen surface
-C3 convertase generated (C4b2a)
-C3 cleaved -> C3a + C3b

Question 24

initiator of classical pathway

Answer 24

C1q

Question 25

what can C1q do:

Answer 25

-C1q binds pathogen surface -Can bind pathogen directly -Can bind antibodies bound to pathogen surface

Question 26

which path way connect adaptive and innate immunity

Answer 26

Classical pathway: -C1q can bind to antibodies bounf to pathogen surface (geenrated by activated B cells -adaptive immunity)

Question 27

what happens once C1q is bound:

Answer 27

-Triggers signaling cascade on pathogen surface C3 convertase generated (C4b2a) C3 cleaved -> C3a +C3b

Question 28

Classical & lectin pathway result in generation of which C3 converts

Answer 28

C4b2a

Question 29

C3a involved in

Answer 29

enhancing inflammation

Question 30

C3b involed in:

Answer 30

opsonization & C5 convertase -> C5a + C5b

Question 31

1st alternative pathway

Answer 31

-Once C3b produces by lectin/classical pathway activation -Amplification loop for C3b formation (depose more C3b on pathogen) -Require factor B & protease factor D -Factor D cleave factor B -> Ba +Bb -makes C3bBb - C3 convertase

Question 32

what does alternative pathway make:

Answer 32

C3bBb - C3 convertase

Question 33

2nd alternative pathway

Answer 33

-When high concentration of C3 (liver produced - inactive) --> undergo spontaneous hydrolysis -Involves factors B & D -makes C3bBb

Question 34

whats different from alternaitve pathway C3 convertase (C3bBb) and classical/lectin pathway C3 convertase (C4b2a)

Answer 34

C3bBb is very unstable

Question 35

how to stabilize C3bBb

Answer 35

-Stabilized by factor P (properdin) secreted by neutrophils -Properdin stabilize C3 convertase as it can bind to some microbial surfaces

Question 36

pathogens are mainly ... for the complement system. why?

Answer 36

extracellular -everything is deposited on the pathigen surface --> phagocytosis -phagocytosis are for extracellular bacteria -MAC formation-pores forming on cell's surface

Question 37

complement system act mainly on:

Answer 37

exracellular pathogens: -phagocytosis -MAC formation

Question 38

Downstream effect of C3 convertase cleaving:

Answer 38

Inflammation Increase phagocytosis Pathogen lysis

Question 39

downstream effect: inflmmation

Answer 39

-Additional signaling = cleavage of other complement molecules -C3a & C5a recruit phagocytes & promote inflammation

Question 40

what happens too much inflammation:

Answer 40

-If present in large amount – C3a & C5a --> anaphylactic shock

Question 41

what happens when promoting inflammation?

Answer 41

-Complement receptors connect complement tagged pathogens to effector cells -C3aR/C5aR on granulocytes -Stimulate release of proinflammatory cytokines & granule components from basophils/eosinophils/neutrophils/mast cells

Question 42

Downstream effect: Increase phagocytosis

Answer 42

-Phagocytes have receptor on C3b -Opsonization of pathogen -Opsonization can happen via complement deposition and/or antibodies (phagocytes also have receptors for antibodies)

Question 43

downstream effect: Pathogen lysis

Answer 43

-Additional complement factors create MAC (membrane-attack complex) -> cell lysis -C5b (directly) & C3b (indirectly) involved -Cascade leading to formation of MAC –

Question 44

Negative regulation of Complement activation: who is responsible

Answer 44

-Complement-regulatory proteins in plasma or cell surfaces

Question 45

Negative regulation of Complement activation: what happens

Answer 45

-prevent complement activation from proceeding normal/basal conditions -Prevent appearance of C3 convertase -Promote disappearance of C3 convertase

Question 46

2 C3 convertase and what do they do

Answer 46

C4b2a & C3bBb cleaves C3 to C3a & C3b

Question 47

C3b role

Answer 47

involved in opsonization & C5 convertase

Question 48

what is C5 convertase involved in

Answer 48

indirectly involved in MAC

Question 49

C3a role

Answer 49

inflammation

Question 50

C5b role

Answer 50

MAC

Question 51

C5a

Answer 51

inflammation