effector mechanisms of humoral immunity: elimination of extracellular microbes and toxins

Question 1

Effector functions of Abs

Answer 1

1. neutralize - microbial toxins
2. opsonize - tags pathogens for ehancing phagocytosis (IgG)
3. sensitize - enhances NK cell kiling of target
4. mediation of phagocytosis (IgG)
5. activation of complement (IgM and IgD)

Question 2

effector functions of Abs are mediated via

Answer 2

Fc (heavy chain contant region) of Ig molecules

Question 3

neutralization

1. blocks the binding of microbes and toxins to cellular ____
2. prevents ____ of microbes from infected to healthy cells

Answer 3

1. receptors
2. spread

Question 4

virulence factors refer to the properties of bacterial gene ____ that enable a microorganism to cause disease

Answer 4

products

Question 5

FcgammaRI has a ____ affinity

Answer 5

high

Question 6

FcgammaRII has a ____ affinity

Answer 6

low

Question 7

FcgammaRIII has a ____ affinity

Answer 7

low

Question 8

FcepislonRI has a ____ affinity

Answer 8

high

Question 9

FcbgammaRIIB:

1. found on ___ cells
2. can bind ____ complexes via Fc portion
3. activates ____ → inhibits signaling in B cell
4. ____ affinity receptor meaning in works later in immune response

Answer 9

1. B cells
2. Ag-Ab
3. phosphatases
4. low

Question 10

isotypes ____ and ____ are the most effiient opsonins for promoting phagocytosis via high-affinity FcgammaRI

Answer 10

IgG3 and IgG1

Question 11

due to its ____ affinity, FcgammaRI works ____ in immune responses

Answer 11

high

early

Question 12

due to its ____ affinity, FcgammaRIIB works ____ in immune responses when large amounts of immune complexes are formed

Answer 12

low

later

Question 13

FcepsilonRI:

1. found on ____ cells and ____
2. bind Fc portion of ____
3. useful in protection against ____
4. when bound to Fc portion of IgE → release cationic protein ( ____ ____ ____ ) that is toxic to worms
5. this happens in immediate reactions due to its ___ affinity

Answer 13

1. mast cells and eosinophils
2. IgE
3. helminths
4. major basic protein (MBP)
5. high

Question 14

antibody dependent cellular cytotoxicity (ADCC):

1. Ab binds to microbe, then Fc portion bind to ____ on ____
2. activates NK cells to kill Ab-coated cells via ____ and ____
3. ____ affinity → works later in immune response

Answer 14

1. FcgammaRIII on NK cells
2. perforin and granzymes
3. low

Question 15

alternative complement pathway:

1. C3 spontaneously celave to ____ on cell surface
2. Factor ____ binds to C3b
3. Factor ____ binds to and cleaves Factor B
4. Factor B is cleaved into ____ and Ba
5. Bb is bound to C3b, forming ____ (C3 alternative convertase)
6. C3 convertase cleaves C3 into ____ and C3a
7. C3b combines with C3bBb forming ____ (C5 convertase)
8. C5 convertase cleaves C5 into ____ and C5a
9. formation of ____

properdin:

Answer 15

1. C3b
2. B
3. D
4. Bb
5. C3bBb
6. C3b
7. C3b3bBb
8. C5b
9. MAC

Properdin: stabilizes the interactions of the alternative pathway

Question 16

classical complement pathway:

1. ____ or ____ bind to the surface of bacterial pathogen
2. ____ binds to staple formation of IgM (sometimes IgG) (bind to Fc portin)
3. C1q activates ____ which activates ____
4. C1s cleaves ____ (into C2a and C2b) and ____ (into C4a and C4b)
5. C4b combines with C2a to form ____ (C3 convertase) (which is deposited on surface)
6. C3 convertase cleaves C3 into ____ and C3a
7. C3b combines with C4b2a to form ____ (C5 convertase)
8. C5 convertase cleaves C5 into ____ and C5a
9. formation of ____

Answer 16

1. IgM or IgG
2. C1q
3. C1r C1s
4. C2. C4
5. C4b2a
6. C3b
7. C4b3b2a
8. C5b
9. MAC

Question 17

lectin complement pathway:

1. ____ ____ ____ binds to the surface of mannose on bacterial walls
2. ____ is bound to the MBL
3. MASP2 cleaves ____ (into C2a and C2b) and ____ (into C4a and C4b)
4. C4b combines with C2a to form ____ (C3 convertase)
5. C3 convertase cleaves ____ into C3b and C3a
6. C3b combines with C4b2a to form ____ (C5 convertase)
7. C5 convertase cleaves ____ into C5b and C5a
8. formation of ____

Answer 17

1. mannose binding lectin
2. MASP2
3. C2 C4
4. C4b2a
5. C3
6. C4b3b2a
7. C5
8. MAC

Question 18

MAC formation:

1. after C5 convertase activity, ____ has binding site for C6
2. when C5b-C6 complex have formed, ____ binds
3. C5b67 complex is bound to membrane via ____
4. ____ binds (allowing for complex to be inserted into the membrane
5. C8 initiates the polymerization of ____
6. ____ polyemizes to form the pore

Answer 18

1. C5b
2. C7
3. C7
4. C8
5. C9
6. C9

Question 19

CR1 functions:

1. promote ____ of C3b and C4b coated particles
2. ____ of immune complexes
3. activates ____ mechanisms of phagocytes

Answer 19

phagocytosis

clearance

killing

Question 20

CR 2:

on ____ lymphocytes

____ affinity for cleavage products of C3b

enhances response of B cell to ____ when bound

associated with ____ infections

Answer 20

B

high

Ag

EBV

Question 21

CR3:

1. can bind ____ (necessary for recruitment of leukocytes
2. binds iC3b to induce ____

Answer 21

1. ICAM-1
2. phagocytosis

Question 22

C1 INH inhibits ____ activation

Answer 22

classical

Question 23

DAF:

1. ____ convertase decay
2. inhibits ____ pathways

Answer 23

C2:C4

classical or alternative

Question 24

CR1

C3 convertase decay – inhibits ____ pathways

Answer 24

all

Question 25

MCP:

____ convertase decay

inhibits ____ pathways

Answer 25

C3

all

Question 26

CD59:

inhibits ____ formation by blocking the addition of ____

Answer 26

MAC

C9

Question 27

complement function: induction of inflamation:

inflammation via ____ , ____ , ____

these proteins active:

Answer 27

C5a, C3a, C4a

mast cells, NPs, and endothelial cells

Question 28

by binding to Ag-Ab complexes, complement promotes ____ of these complexes and their clearance by phagocytes

Answer 28

solubilization

Question 29

____ deficiency is the most common human complement dificiency

Answer 29

C2

Question 30

systemic lupus erythematosus:

1. complement deficiency:
2. effect:

Answer 30

1. C1q, C2, C4
2. failure of clearing immune complexes; will be deposited on blood vessels and lead to inflammation

Question 31

pyogenic bacterial infections:

1. complement deficiency:
2. effect:

Answer 31

1. C3
2. can be fatal, inability to produce complement activities

Question 32

deficiencies in ____ and ____ result in increased susceptibility to infection with pygoenic bacteria

Answer 32

properdin and factor D

Question 33

neisseria bacteria:

complement deficiency:

Answer 33

C5-C9

Question 34

pathologies of complement:

1. complement system can cause sigificant tissue ____
2. complement activation is associated with intravascular ____ and can lead to ____ injury to tissues
3. can lead to ____ (MAC mediated)

Answer 34

1. damage
2. thrombosis ischemic
3. neuropathies

Question 35

evasion of complement of microbes:

1. microbes can evade the complement system by recruiting host:
2. many pathogens express ____ acids which can inhibit the alternative pathway of complement by recruiting factor ____ which displaces C3b from Bb
3. example: HIV incorporate host regulatory proteins ____ and ____ when it buds from an infected cell

Answer 35

1. complement regulatory proteins
2. sialic H (which removes C3b from Bb)
3. DAF and CD59

Question 36

neonatal immunity:

1. transport of maternal ____ across the placenta and across the neonatal intetinal epithelium is mediated by ____
2. maternal ____ in breast milk in ingested by infant
3. Abs in breast milk are transported across the gut epithelium by a process known as ____

Answer 36

1. 1. IgG FcRn
2. IgA
3. transcytosis