Thrush- Complement Cascade

Question 1

what are the functions of the complement cascade?

Answer 1

causes cell lysis, results in opsonization (tagged substance removed by phagocytic cells) of Ag and mediates inflammation

Question 2

if a cell is going to be lysed, what are the membrane attack complexes (MAC) that need to be used?

Answer 2

MAC C5b-C9

Question 3

of the 30 different proteins required for the complement cascade activation, which area of the body is most important site of synthesis for these proteins?

Answer 3

the liver

Question 4

once the proteins are activated they are generally split into components. which of the fragments is more likely to stimulate inflammation and which is likely to remain bound to the target cell?

Answer 4

smaller fragment-> inflammation

larger fragment-> bind to target cell

Question 5

what antibodies can activate the classical pathway? and what regions have to be close to C1 to help activation?

Answer 5

IgG and IgM.

multiple Fc regions (at least 2) need to be in close proximity C1 for binding and then activation

Question 6

if a patient has a mutation for a faulty C3, how will the complement cascade be affected?

Answer 6

the complement cascade wont work because C3 is the branch point

Question 7

what is the importance of C3a?

Answer 7

is stimulates inflammation

Question 8

how is the alternative pathway activated?

Answer 8

by surface components (bacterial LPS, cell wall components) binding to C3b

Question 9

the MBP (lectin) pathway is activated by what?

Answer 9

collectins like Mannan-binding protein that activate the cascade by binding a microbe to its lectin binding domain and having cell interaction at its collagen domain

Question 10

is it more likely that the classical pathway be activated via IgM binding or IgG binding?

Answer 10

IgM because it contains 5 Fc regions in one molecule, where as 2 IgG molecules would need to be next to each other for possible activation

Question 11

what binds to Ch2 in the classical pathway? and upon binding what does it allow to take place?

Answer 11

C1q binds to Ch2.

upon binding C1r activates C1s

Question 12

what does C1s activate? and how does it lead to the production of an enzyme?

Answer 12

activates C4 and C2.

C4b then binds to C2a (C4a and C2b float and diffuse away respectively). C3 convertase is the product of C4b2a

Question 13

C3 is cleaved by C3 convertase. but which subunit (C3b or C3a) binds with C4b2a to form C5 convertase? what happens with the other subunit?

Answer 13

C3b binds to C4b2a to form C5 convertase.

C3a diffuses away to become an inflammatory meidator

Question 14

what creates the Membrane attack complex (MAC)? and what does it cause?

Answer 14

when C5b binds C6, C7, C8, C9.

causes lysis

Question 15

in the alternative pathway what are some initiators?

Answer 15

LPS, teichoic acid (gram positive bacteria), zymosan (fungal/yeast wall), viruses, parasites, human IgG, IgA and IgE complexes

Question 16

in alternative pathway what is spontaneously hydrolyzed? and what subunit that it produces binds to a foreign surface?

Answer 16

C3.

C3b binds to foreign surface

Question 17

after the MBP pathway is activated, what other pathway does it mirror?

Answer 17

classical pathway (MBP acts like C1 and activates C2 and C4)

Question 18

what is the purpose of C3a, C4a and C5a in C’ activation?

Answer 18

inflammation (degranulation/ extravasation)

Question 19

what is the main function of C3b and C4b in C’ activation?

Answer 19

opsonization (increase phagocytic cell recognition/ destruction of Ag)

Question 20

what types of microbes can evade complement proteins/pathways?

Answer 20

long chain polysaccharides to LPS, outermembrane proteins, elastase, thick peptidoglycan layer, capsules (decreases opsonization) and proteins that mimic C’ proteins (inhibitory)