Soluble mediators

Question 1

how are defensins and histatins activated ?

Answer 1

by proteolysis to release an amphipathic antimicrobial peptide.

Question 2

what does the skin contain to protect against pathogen ?

Answer 2

fatty acids
B defensins
lamellar bodies
cathelicidins

Question 3

how are the epithelial cells joined ?

Answer 3

by tight junctions to try to keep pathogens out

Question 4

what does the gut contain?

Answer 4

tight junctions by epithelial
longitudial flow of air 
low pH 
enzyme pepsin 
alpha defensins such as cryptidins

Question 5

the gut has regIII , what is this ?

Answer 5

an antimicrobial peptide

Question 6

what do the lungs contain ?

Answer 6

longitudinal flow of air
epithelial cells joined by tight junctions
cillia to move mucus to be excreted
primary surfactant to produce a sterile environment

Question 7

what contains lysozyme ?

Answer 7

the tears and saliva stored in lysosomes

Question 8

what is the function of lysozyme ?

Answer 8

it breaks down carbohydrate chains and breaks the integrity of the bacterial outer membrane . The bacteria then burst under their own internal pressure.

Question 9

how do defensins work ?

Answer 9

The defensin has a positive charge and this is drawn to the electrostatic attraction of the lipid bilayer and it forms a pore with it’s peptide to disrupt the bilayer.

Question 10

how do cathelicidins work ?

Answer 10

These are stored in neutrophil granules as inactive precursors (prepropeptides) . They are released when cleaved by neutrophil elastase , this then results in the disintegration of the pathogen cell membrane.

Question 11

what is a complement ?

Answer 11

a collection of serum proteins that protect against infections / abnormal cells , they initiate a cascade effect which amplifies the initial responses.

Question 12

the complement proteins interact with the immune complexes , what ones?

Answer 12

IgM and IgG antigen

Question 13

whats the 2 things that the complement proteins do ?

Answer 13

lysis – complete pathway to produce membrane attack complex.

– act as a bridge with an innate cells to allow close contact – complement-mediated cytotoxicity.

Question 14

why does the complement pathway have three pathways for activation ?

Answer 14

if we just had one and the pathogen evaded this then it wouldn’t be beneficial to just have one.

Question 15

in .the complement pathways what is A normally ?

Answer 15

small product except C2 where C2a is big molecule

Question 16

what do the A products normally initiate ?

Answer 16

inflammatory response by binding to specific receptors such as complement component 3a receptor 1 and complement component 5a receptor 1

Question 17

in the complement pathway what is b normally ?

Answer 17

BIG product - bind to targets near activation sites

Question 18

what does b product initiate ?

Answer 18

and they interact with cell surface receptors to promote phagocytosis through osponisation.

Question 19

what’s the 3 complement pathways ?

Answer 19

Classical
Alternative
Lectin

Question 20

what does the classical pathway require ?

Answer 20

antibodies IgG and IgM

Question 21

what is the classical initiated by ?

Answer 21

C1 components

Question 22

what does the C1q bind to and what occurs next ?

Answer 22

the Fc portion of IgM and IgG which then binds to C1r and C1s to form complex C1

Question 23

what does the C1 enzyme cleave ?

Answer 23

c4 to make c4a ( inflammation mediatior ) and c4b ( opsonise) as well as C2 to C2a and C2b

Question 24

what does C4b bind to ?

Answer 24

the pathogen to opzonise it and then binds to C2

Question 25

what cleaves c3?

Answer 25

the complex c4b2a convertase

Question 26

what does C3 cleave into ?

Answer 26

c3a and C3b

Question 27

what does c3a do ?

Answer 27

peptide mediator of inflammation

Question 28

what does C3b do ?

Answer 28

binds to the pathogen surface and acts as a opsonisation for phagocytosis

Question 29

what is the C5 convertase ?

Answer 29

c3b

Question 30

what does C5b bind to ?

Answer 30

the surface of the pathogen and then binds C6 , C7 and C8 and a number of monomers of C9 to form C5b-9 .

Question 31

what does C5b-9 do ?

Answer 31

it results in cell lysis of gram negative bacteria and pores form .
Inflammation also occurs.

Question 32

what does the alternative pathway require ?

Answer 32

bacteria

Question 33

what is alternative initiated by and what happens?

Answer 33

C3 and spontaneous hydrolysis to C3(h20)

Question 34

when C3 is enzmatically cleaved what does this result in ?

Answer 34

c3b

Question 35

what does c3b do ?

Answer 35

C3b binds to serum protein called Complement factor B form C3Bb complex. Exposes a site on Factor B that is a substrate for Complement factor D.

Question 36

what does factor D do ?

Answer 36

cleaves factor B to Ba and Bb

Question 37

C3Bb and 3b form what ?

Answer 37

C3Bb3b - C5 convertase.

Question 38

what occurs if no stabilisation occurs to the complement factor properdin when binds to C3Bb ?

Answer 38

then the convertase will break up .

Question 39

what does C5b bind to ?

Answer 39

C6 , C7 , C8 and C9 to form C5b-p membrane attack complex

Question 40

what is the lectin pathway initiated by ?

Answer 40

mannose binding lectin ( MBL) binding to the mannose residues on the pathogen surface , this causes MASP 1 and MASP2 to be activated which are proteases.

Question 41

what does MASP-2 do ?

Answer 41

it cleaves C4 to C4a and c4b and C2 to C2a and C2d. C3 convertase C4b2a forms it cleaves C3 and c5 convertase forms which cleaves C5 to C5b which joins with the C6 , C7,C8 and C9 C5b-9.

Question 42

do bacteria contain lots of mannose residues on their surface ?

Answer 42

YES