Complement

Question 1

what is complement

Answer 1

very complex system of 50 diff proteins in serum or receptors on white cells
wide rage functions
involves enzyme cascade

Question 2

what do all components of enzyme cascade do

Answer 2

circulate as inactive precursors

makes proteolytic enzymes activating other enzymes

Question 3

what is the central protein of complement

Answer 3

C3

Question 4

what does a deficiency of C3 lead to

Answer 4

recurrent bacterial infections

Question 5

what do all three complement pathways result in

Answer 5

proteolytic cleavage of C3 to C3b and C3a

Question 6

what is C3b and C3a

Answer 6

C3b - large fragment

C3a - small fragment

Question 7

what does C3b then do after having been cleaved

Answer 7

deposited onto surface of micro organism and marks it out for destruction via lysis or opsonisation

Question 8

what enzyme is used during cleavage

Answer 8

C3 convertase

Question 9

where is a thioester bond

Answer 9

between Cys and Glu on alpha chain

Question 10

after cleavage what happens to the thioester bond

Answer 10

becomes exposed and unstable

nucleophilic attack by electrons on -OH and -NH2 group

Question 11

what happens after the thioester bon is nnucelophillic attacked

Answer 11

covalent bond formed to membrane of pathogens

Question 12

what is the first component of the classical pathway

Answer 12

C1q

Question 13

what is C1q

Answer 13

hexavalent
base - collagen like triple helices
stalk - triple helices
globular heads

Question 14

what do the globular heads of C1q do

Answer 14

bind Fc of IgG or IgM

Question 15

what is the classical pathway activated by

Answer 15

IgG r IgM

Question 16

what binds C1q

Answer 16

C1r or C1s

Question 17

what do C1r and C1s become

Answer 17

proteolytic enzymes

lead to C4 and C2 cleaved and C3 cnvretase formed

Question 18

proteolytically active C1 cleaves what

Answer 18

C4 into C4a and C4b - bind to mem of pathogen and recruit C2

Question 19

what forms C3 converts

Answer 19

C4b2a

Question 20

what is MBL

Answer 20

mannose binding lectin

Question 21

what is the caacteristics of MBL

Answer 21

bouquet like C1q

bind sugar mols found in repeating arrays on microbial surfaces

Question 22

are there antibodies involved in lectin pathway

Answer 22

no only in classical

Question 23

what is the lectin pathway

Answer 23

MBL-MASP-2 complex bind C4

C2 comes along and for C3 convertase

C3 cleaved and C3b fragments bind to surface

Question 24

whats the alternative pathway

Answer 24

also prod C3 convertase but uses diff proteins

Question 25

what is the alternative pathway actitved by

Answer 25

many types of microorganisms - bacteria, yeast, trypanosomes

Question 26

when can the alternative pathway function

Answer 26

immediately before Ab response hence first line defenceagaisnt systemic infection

Question 27

what initiates alternative pathway

Answer 27

form and action of soluble C3 convertase iC3b

Question 28

how does C3 become iC3b

Answer 28

spontaneous hydrolysis of thioester bond and factor B binding

Question 29

how is C3b which covalently bonds to pathogen surface made from iC3b

Answer 29

cleavage of factor B by factor D | a c3 convertase some of C3b fromed

Question 30

what si the makeup of C3 conertase fro alternative pathway

Answer 30

C3bBb

Question 31

what does C3b cleave

Answer 31

C5 to C5b and C5a

Question 32

what does C5b do

Answer 32

bids to surface micro organisms

Question 33

four other proteins C6, C7, C8 and C9 form

Answer 33

membrane attack complex which forms funnel shaped hole in cell mem

Question 34

what is opsonisation

Answer 34

coating of micro organisms by antibody or complement components

Question 35

what receptors d phagocytes have

Answer 35

C3b receptors

Question 36

what are the anaphylatoxins

Answer 36

C3a and C5a

Question 37

what does C3a do as an anaphylatoxin

Answer 37

binds to receptors on mast cells histamine release increase vasc perm recruit other components of inflam response to infection site

Question 38

what do anaphlatoxins act directly on

Answer 38

blood vessels increasing blood flow and vasc perm

Question 39

what does C5a trigger

Answer 39

phagocyte chemotaxis

Question 40

what does C5a bind to

Answer 40

C5a receptors on phagocytes phagocyte migrates up concentration gradient of C5a to infection site phagocyte becomes stickier phagocyte stop moving

Question 41

what controls the classical pathway

Answer 41

C1 inhibitor Decay accreting factor complement receptor 1

Question 42

what controls the alternative pathway

Answer 42

Factor I Factor H CR1

Question 43

what can some micro organisms do

Answer 43

avoid effects of complement

Question 44

what else does complement do

Answer 44

removing immune complexes

Question 45

deficiencies in classical pathway components assc with

Answer 45

immune complex autoimmune diseases

Question 46

how does complement rid of Ic

Answer 46

IC bind to RBC and phagocytes via complement receptor and eliminate