Chapter 12 - B Cells Part 1

Question 0

What can the progeny of a B cell clone differentiate into?

Answer 0

1) plasma cell that produces IgM
2) Isotype switching (IgG)
3) affinity maturation
4) Memory B cell

Question 1

How is a B cell activated?

Answer 1

recognition of Ag by surface BCRs with the help of T helper cells
it stimulates proliferation and then differentiation

Question 2

Where do mature B cells develop from in the absence of Ag?

Answer 2

bone marrow

Question 3

What does Ag bind to on mature, naive B cells?

Answer 3

membrane IgM and IgD

Question 4

what is affinity maturation?

Answer 4

activated B cells producing Abs that bind to Ags with increasing affinity progressively dominate the response

Question 5

T-dependent Ags are characteristic of what?

Answer 5

proteins, require CD4 T helpers

Question 6

what kind of cell facilitates the formation of Germinal Centers?

Answer 6

follicular helper T cell

Question 7

where are GCs located?

Answer 7

secondary lymphoid organs

Question 8

In T-dependent responses, activated B cells differentiate into what?

Answer 8

Ab-secreting plasma cells

Question 9

where do plasma cells migrate from and to where?

Answer 9

from GCs to bone marrow

Question 10

What are T-independent Ags?

Answer 10

multivalent non-protein Ags

ex. polysaccharides, lipids, nucleic acids

Question 11

What is typically seen in humoral immune responses to protein Ags?

Answer 11

isotype switching and affinity maturation

Question 12

how does a primary immune response work?

Answer 12

naive B cells are stimulated by Ag, become activated, and differentiate into Ab-secreting cells

Question 13

how do secondary immune responses work?

Answer 13

Ag stimulates memory B cells, leads to greater production of specific Abs, develops more rapidly, T-dependent

Question 14

What initiates T-dependent Ab responses?

Answer 14

Follicular B cells

Question 15

what mediates T-independent responses to multivalent Ags?

Answer 15

Marginal zone B cells in the spleen

B-1 cells in mucosal sites

Question 16

In secondary lymphoid tissues, follicular B cells migrate where?

Answer 16

to B cell zones of these tissues called follicles

Question 17

what guides this movement into follicles?

Answer 17

CXCL13, secreted by DCs

Question 18

what does CXCL13 attract?

Answer 18

naive B cells

Question 19

what kind of Ags may reach the B cell zone of the follicle directly?

Answer 19

soluble, small (less than 70 kD) Ags

Question 20

how are microbes and Ag-Ab complexes transported to B cell zones?

Answer 20

by subcapsular sinus macrophages

Question 21

how are large Ags transported into follicles to activate B cells?

Answer 21

by resident DCs

Question 22

In the spleen, Ags may bind CR2 on what?

Answer 22

marginal zone B cells

Question 23

what do plasmacytoid DCs capture and where do they deliver their contents to?

Answer 23

blood-borne pathogens and transported to the spleen, where they may be delivered to marginal zone B cells

Question 24

How must the Ag presented to B cells be?

Answer 24

unprocessed, in native conformation, intact, soluble

Question 25

what cytokine signals for follicular B cell survival? where is it produced? what receptor is used to provide maturation and survival signals?

Answer 25

BAFF, produce by myeloid cells in lymphoid follicles BAFF receptor

Question 26

what makes up the Ag receptor complex of mature B cells?

Answer 26

Ag bound to membrane Ig molecules | Igalpha and Igbeta proteins

Question 27

what happens if the Ag is a protein?

Answer 27

processed and presented (class II MHC) on the B cell surface for recognition by T helper cells

Question 28

How is B cell activation facilitated (2 ways)?

Answer 28

CR2/CD21 coreceptor on B cells PAMP recognition and TLR signaling

Question 29

what may also activate complement, which explains why Ags are able to induce Ab responses without T cell help?

Answer 29

non-microbial polysaccharides

Question 30

Ag-induced cross-linking of the BCRs induces what cellular responses?

Answer 30

1) increased survival and proliferation 2) costimulation and interaction with helper T cells 3) increased responsiveness to cytokines 4) migration from follicle to T cell areas due to increased expression of CCR7

Question 31

B-T cell interaction in extrafollicular sites leads to what?

Answer 31

isotype switching and short-lived plasma cell generation

Question 32

what event occur in germinal centers?

Answer 32

somatic mutation, affinity maturation, isotype switching, memory B cell generation, long-lived plasma cells

Question 33

what happens in response to hapten-carrier conjugates?

Answer 33

hapten recognized by a specific B cell, conjugate is endocytosed, carrier protein is processed in the B cell, and the peptides from the carrier are presented to the helper T cell

Question 34

Where is CD40L expressed? CD40? what does this stimulate?

Answer 34

Helper T cell B cells B cell proliferation and differentiation

Question 35

what TF is required for T-independent Ags? T-dependent?

Answer 35

Blimp-1 Bcl-6

Question 36

within the Germinal center, what does the dark zone contain? | light zone?

Answer 36

proliferating B cells (undergo isotype switching and somatic hypermutation of Ig V genes) follicular DCs (display Ag and T (FH) cells)

Question 37

What do follicular Helper T cells express?

Answer 37

ICOS, PD-1, IL-21, Bcl-6

Question 38

how are follicular helper t cells generated?

Answer 38

DC, then activated B cell TFH migrate into GCs where they activate B cells

Question 39

What is secreted by TFH cells? What do the secretions do?

Answer 39

IL-21 - required for GC development and generation of plasma cells IFN-gamma or IL-4: controls isotype switching