Lecture 13: Effector Mechanisms of Humoral Immunity

Question 1

functions of antibodies against microbes and their toxins

Answer 1

• Neutralize these agents
• Opsonize them for phagocytosis
• Sensitize them for Ab-dependent cellular cytotoxicity
• activate the complement system
• (note that the various functions are mediated by different Ab isotypes)

Question 2

Question 3

The influenza viruses use their envelope _______ to infect respiratory epithelial cells

Answer 3

Hemagglutinin

Question 4

What are virulence factors

Answer 4

• refer to the properties of bacterial gene products that enable a microorganism to cause disease

Question 5

Question 6

Isotypes ____ and ___ are the most efficient opsonins for promoting phagocytosis via high-affinity FcgammaRI (CD64)

Answer 6

• IgG1
• IgG3

Question 7

A polymorphism in the ______ gene has been linked to susceptibility to the autoimmune disease systemic lupus erythrematosus in humans

Answer 7

• FcgammaRIIB gene
• (this makes sense because they are not able to activate the inhibitory (FcgammaRIIB) thus they overproduce antibodies

Question 8

What is antibody-dependent cell-mediated cytotoxicity (ADCC)

Answer 8

• Ab of certain IgG subclasses bind ot infected host cells, and the Fc regions of the bound Ab are recognized by an FcgammaRIII on NK cells
• The NK cells are activated and kill Ab-coated cells

Question 9

Worms can be killed by a toxic cationic protein, known as the _______, present in the granules of eosinophils

Answer 9

Major basic protein (MBP)

Question 10

FcepsilonRI binds to ____ and is found on

Answer 10

• Monomeric IgE
• Found on Mast cells, Basophils, and Eosinophils
• thus needed to fight parasitic infection

Question 11

Question 12

Question 13

The classical pathway is initiated by binding of the ____ to ___ or ___ molecules that bound Ag

Answer 13

The classical pathway is initiated by binding of the C1 to IgG or IgM molecules that bound Ag

Question 14

Among the various IgG subclasses, ____ and ____ are most efficient activators of complement

Answer 14

IgG3 and IgG1

Question 15

C1 is composed of what 3 subunits

Answer 15

• C1q, C1r, and C1s
  
  • The C1q binds to Ab, whereas C1r and C1s are proteases

Question 16

What is the classical pathway C5 convertase

Answer 16

C4b2a3b

Question 17

What is the classical pathway C3 convertase

Question 18

The lectin pathway is triggered by the binding of

Answer 18

microbial polysaccharides to circulating lectins, such as plasma mannose-binding lectin (MBL)

Question 19

which of the MASPs actually cleaves C4 in the lectin pathway

Answer 19

MASP3

Question 20

What are the two componets of the MAC compliment proteins that are in the cell membrane

Answer 20

C7 and C8

Question 21

Compliment receptor 1 (CR1) is found on what cell and what functions does it have

Answer 21

Question 22

CR2: cell distribution and functions

Question 23

CR3 and CR4 cell distribution and fuctions

Answer 23

Question 24

What is the difference between CD59 and S protein

Answer 24

• They both inhibit the formation of the MAC complex but do it in different ways
• CD59 is a membrane protein that inhibits C9 from foring the MAC
• S protein in the plasma stops the addition of C8

Question 25

What complement deficiency is most common

Answer 25

C2 deficiency

Question 26

C1q, C2, and C4 deficiencies are associated with

Answer 26

* systemic lupus erythematosus * this is because complement activation defects lead to failure to clear circulating immune complexes. Complexes may be deposited in blood vessel walls and tissues, where they produce local inflammation

Question 27

C3 deficiency is associated with frequent serious

Answer 27

pyogenic bacterial infections that may be fatal

Question 28

MAC comlement proteins (C5,C6,C7,C8,C9) deficiences may result in infections by

Answer 28

Neisseria bacteria

Question 29

Many pathogens express ____ , which can inhibit the alternative pathway of complement by recruiting Factor H, which displaces C3b from Bb

Question 30

HIV incorporates what complement regulatory proteins when it buds from an infected cell

Answer 30

* DAF and CD59

Question 31

Transport of maternal IgG across the placenta and across the neonatal intestinal epithelium is mediated by an IgG-specific receptor called

Answer 31

neonatal Fc receptor (FcRn)

Question 32

maternal ___ in breast milk are ingested by the nursing infant

Answer 32

IgA.

Question 33

Question 34

Question 35

Question 36

Question 37

Complement activation is associated with intravascular thrombosis and can lead to

Answer 37

ischemic injury to tissues

Question 38

In an autoanitbody-mediated kidney disorder, membranous nephropathy, damage to glomerular epithelial cells can be mediated by the ____ that is generated after Ab binds to a glomerular auto-Ag

Answer 38

MAC

Question 39

Many pathogens express \_\_\_\_\_, which can inhibit the alternative pathway of complement by recuriting Factor H.

Answer 39

* Sialic acids * (note: factor H binds C3b and displaces Bb, cofactor for facor I, which cleaves C3b and C4b)