Chapter 12 - B Cells Part 2

Question 0

How many constant regions do IgE and IgM have?

IgA, IgD, IgG?

Answer 0

4

3

Question 1

How do you transition from a membrane IgM to a secreted IgM?

Answer 1

lose transmembrane and cytoplasmic segments

Question 2

What happens in the Fab region?

Fc portion?

Answer 2

Ag binding

Effector function

Question 3

What is Ig class switching driven by and where does it happen?

what happens in Ig class switching?

Answer 3

by TFH cells in the GC

changing the Constant region of the heavy chain

Question 4

TRUE or FALASE?

Antigen specificity is changed with class switching.

Answer 4

FALSE

variable region unchanged, but can interact with different effector molecules

Question 5

B cells in mucosal tissues switch to what?

What cytokines stimulate the switch?

Answer 5

IgA

TGF-beta, BAFF

Question 6

CD40 signals work to induce isotype switching with what enzyme?

what is the enzyme need for?

Answer 6

activation-induced deaminase (AID)

isotype switching and affinity maturation

Question 7

immunodeficiencies are dominated by what Igs?

Answer 7

IgM

Question 8

Where does CSR take place and what does it change?

Answer 8

activated B cells

changes CH gene

Question 9

where does CSR take place between?

Answer 9

2 switch regions (S) with looped-out deletion

Question 10

What is the CSR preceded by?

what do these structures open?

Answer 10

germline transcripts

the chromatin structure of a specific S region, recombinase can activate

Question 11

explain the CSR mechanism

Answer 11

AID activated by CD40 and TFH cells
AID deaminates cytosine in ssDNA (C–>U)
UNG removes U, APE1 endonuclease creates nicks that lead to ds break

Question 12

what is affinity maturation?

is it T-dependent or T-independent?

Answer 12

process that leads to increased affinity of Abs for a particular Ag

T-dependent protein

Question 13

What is required for somatic mutation to be initiated?

Answer 13

CD40-CD40L and helper T cells

Question 14

Where does somatic hypermutation occur and is of what type of genes?

what is the result?

Answer 14

GC, of Ig V genes

production of Abs with high affinity for Ag

Question 15

In proliferating GC B cells in the dark zone, what is happening at an extremely high rate?

Answer 15

Ig V genes undergo point mutations

Question 16

what is mutation in Ig V genes called?

Answer 16

somatic hypermutation

Question 17

Where do mutations cluster?

what has more mutations: IgG or IgM?

Answer 17

in V regions, mostly in the Ag-binding CDRs

IgG

Question 18

Where does B cell apoptosis occur?

What stimulates class switching?

Answer 18

GC

TFH

Question 19

Where do B cells that have undergone somatic mutation migrate to?

Answer 19

the FDC-rich light zone of the GC

Question 20

When are B cells with high-affinity receptors for the Ag best able to bind the Ag?

Answer 20

when the Ag is present at low [ ]’s by follicular DCs

Question 21

what are the B cell survival mechanisms?

Answer 21

1) Bcl-2 expression
2) Presentation of Ag for TFH cells in the GC which signal CD40L
3) High affinity B cells activate endogenous inhibitor of Fas

Question 22

Where do B cell lymphomas develop from?

what are they caused by?

Answer 22

GC B cells

chromosomal translocations of oncogenes into Ig gene loci

Question 23

what are the 2 types of plasma cells?

Answer 23

short lived and long lived

Question 24

What are the characteristics of short-lived plasma cells?

Answer 24

T-independent, extrafollicular, found in 2ndary lymphoid organs and peripheral non-lymphoid tissues

Question 25

what are the characteristics of long-lived plasma cells?

Answer 25

T-dependent | generated by signals from BCR and IL-21 via plasmablasts

Question 26

Where are plasmablasts generated? Where do they home?

Answer 26

GC, enter circulation to home to bone marrow and differentiate into long-lived plasma cells

Question 27

how are plasma cells maintained?

Answer 27

BAFF

Question 28

What % of Ab in the blood is produced by long-lived plasma cells?

Answer 28

50

Question 29

Where are memory cells generated from? what do they express high levels of?

Answer 29

GC for T-dependent Ag Bcl-2

Question 30

Memory cells typically express what kind of Ag receptors and what kind of Ig molecules?

Answer 30

high affinity (mutated) receptors switched isotype molecules

Question 31

What do effective vaccines against microbes and toxins require?

Answer 31

affinity maturation AND memory B cell formation

Question 32

What are conjugate vaccines? what do they more readily induce?

Answer 32

polysaccharides covalently linked to a foreign protein to form a hapten-carrier equivalent high-affinity Abs and memory cells

Question 33

What are TI characteristics?

Answer 33

multivalent, low level isotype switching (IgM), little or no affinity maturation

Question 34

What are TD characteristics?

Answer 34

proteins, lots of isotype switching, allows affinity maturation and secondary responses

Question 35

How do TI Ags become activated with T cell help?

Answer 35

maximal cross-linking of the BCR complex on B cells

Question 36

Where are TI Ab responses initiated?

Answer 36

spleen, bone marrow, peritoneal cavity, and mucosal sites

Question 37

What kind of B cells are especially important for Ab responses to TI ags?

Answer 37

Marginal zone and B-1

Question 38

what do marginal zone b cells mainly respond to? what do they differentiate into after activation?

Answer 38

polysaccharides short-lived plasma cells that secrete IgM

Question 39

Where may TI Ags persist for long periods of time?

Answer 39

surface of marginal zone macrophages in the spleen

Question 40

What do B-1 cells respond to?

Answer 40

TI Ags in the peritoneum and mucosal sites

Question 41

What do TI Ags of polysaccharide nature activate?

Answer 41

complement system via alternate pathway | generate C3d, binds to Ag, recognized by CR2 on B cell

Question 42

what is the dominant Ab class induced by pneumococcal capsular polysaccharide?

Answer 42

IgG2

Question 43

BAFF produced by DCs and macrophages induces synthesis of what? what facilitates this?

Answer 43

AID in Ag-activated B cells activation of TLR on B cells

Question 44

what mediates IgA switching?

Answer 44

TGF-beta

Question 45

what is the major mechanism of host defense against infections by encapsulated bacteria?

Answer 45

humoral immunity

Question 46

what contributes to the generation of natural Ab?

Answer 46

TI Ags

Question 47

most Abs are ______ produced by ______ stimulated by _____

Answer 47

low affinity anti-carb Abs peritoneal B-1 cells Marginal Zone B cells in the spleen

Question 48

Blood group Ags are important for what but not important for what?

Answer 48

imp: blood transfusions and transplantation NOT: host defense

Question 49

what do polysaccharide vaccines induce?

Answer 49

long-lived protective immunity

Question 50

what happens in b cell activation involving PIP3?

Answer 50

BCR --> PIP3 --> B cell activated

Question 51

what is the mechanism of the FcgammaRIIB receptor?

Answer 51

SHIP converts PIP3 --> PIP2 in BCR complex this blocks b cell receptor signaling and there is no activation phosphatases of the Fcg... tail inhibit signaling in the BCR complex