Humoral Immunity (Exam 2)

Question 1

(T/F) All antibody isotypes have the function to neutralize microbes and toxins.

Answer 1

True

Question 2

What are the 3 ways antibodies can neutralize microbes and toxins?

Answer 2

1. block microbe from getting through epithelial barrier
2. block microbe binding to host cell
3. block toxin from binding to cell receptor

Question 3

List the 5 antibody isotypes.

Answer 3

IgG
IgA
IgM
IgE
IgD

Question 4

What is the major function of IgM?

Answer 4

activate complement (classical pathway)

Question 5

List the 5 major functions of IgG.

Answer 5

1. opsonization + phagocytosis
2. activate complement (classical path)
3. cytotoxicity (NK cells)
4. neonatal immunity
5. feedback inhibition of B cell activation

Question 6

What is the major function of IgA

Answer 6

1. mucosal immunity (GI + respiratory)

Question 7

Where does IgA function to neutralize microbes?

Answer 7

in lumen of mucosal organs

Question 8

What are the 2 major functions of IgE?

Answer 8

1. helminth defense
2. mast cell degranulation

Question 9

What is the function of IgD?

Answer 9

functions as antigen receptor on B cells (not well known)

Question 10

_____ receptors are proteins on cell surfaces that recognize specific ____ regions on antibodies to help with immune response.

Answer 10

Fc
Fc (constant)

Question 11

(T/F) Free or circulating antibodies are activated by Fc receptors.

Answer 11

False - antigen-bound

Question 12

What two antibody isotypes are involved in the two major types of antibody dependent cell-mediated cytotoxicity?

Answer 12

IgG
IgE

Question 13

In the IgG cytotoxicity process, Fc regions on IgG are recognized by _____ receptor on ______ cells which kills antibody-coated cells.

Answer 13

Fcy (gamma)
NK cells

Question 14

In IgE cytotoxicity process, IgE binds to _______ and Fc regions on IgE are recognized by ____ receptor on _______ which cause death when they release granules.

Answer 14

helminth parasites
Fce (epsilon)
eosinophils

Question 15

What are the 3 complement pathways?

Answer 15

1. classical
2. alternative
3. lectin

Question 16

How is the classical complement pathway activated?

Answer 16

when antibody binds to antigen (IgG + IgM)

Question 17

How is the alternative complement pathway activated?

Answer 17

on microbial cell surface w/o antibody

Question 18

How is lectin complement pathway activated?

Answer 18

plasma lectin binds to mannose receptors on microbe surface

Question 19

What are the C3 convertases for each complement pathway?

Answer 19

classical & lectin: C4b + 2a
alternative: C3b + Bb

Question 20

Why does soluble IgG not activate complement?

Answer 20

only has one Fc region

Question 21

What must occur for IgG to activate complement?

Answer 21

must bind to cell surface (then adjacent IgG Fc regions can bind complement)

Question 22

(T/F) Both soluble IgM and IgA cannot activate complement.

Answer 22

False- IgM + IgG cannot

Question 23

Why can soluble IgM not activate complement?

Answer 23

Fc regions are pentameric so not accessible to complement

Question 24

What must occur for soluble IgM to activate complement?

Answer 24

binds to cell surface and then can change conformation

Question 25

What does MAC stand for?

Answer 25

membrane attack complex

Question 26

What is Membrane Attack Complex?

Answer 26

protein complex (of different complements) that can lyse cells

Question 27

MAC is the (first/last) step in complement activation.

Answer 27

Last

Question 28

Which complements (in order of formation) bind together to form MAC?

Answer 28

C5b, C6, C7, C8, C9

Question 29

List the 3 major functions of complement.

Answer 29

1. opsonization + phagocytosis 2. inflammation 3. cytolysis

Question 30

In terms of complement's function to opsonize and phagocytize microbes: cell -bound ______ is an opsonin which promotes phagocytosis of coated cells.

Answer 30

C3b

Question 31

What 3 proteolytic products stimulate leukocyte recruitment and inflammation (one of the functions of complement)?

Answer 31

C5a, C3a, C4a

Question 32

One function of complement is cytolysis via ________.

Answer 32

MAC (membrane attack complex)

Question 33

_____ is transported through epithelial cells to neutralize microbes before they invade the epithelium.

Answer 33

IgA

Question 34

IgA binds to ______ receptor and then is transported through the epithelial cell. Proteolytic cleavage occurs which allows it to become released into the lumen.

Answer 34

Poly-Ig