B Cell Development and Activation Flashcards Preview

MSS-IHL Final Exam > B Cell Development and Activation > Flashcards

Flashcards in B Cell Development and Activation Deck (49):
1

mature naive B cells possess what surface markers?

IgM and IgD
Ig-alpha and Ig-beta
CD19 and CD20
CR2
MHC Class I and II

2

where do mature naive B cells migrate?

most to secondary lymphoid organs
-lymph nodes and spleen

enter through HEVs and circulate for weeks

if not activated, die by apoptosis

3

B-1 cells

develop from the fetal liver-derived stem cells
-find in the GALT

respond to non-protein antigen in mucosa

have the CD5 marker**

4

B-2 cells

develop from B cells produced after birth

are follicular and marginal

5

follicular B cells

subset of B-2 cells
**major subset

re-circulating cells (surveillance)

6

margin B cells

subset of B-2 cells
reside in the spleen

don't recirculate

more likely to respond to blood-borne polysaccharides**

7

what is necessary for signal transduction of B cells?

Ig alpha and beta dimer is necessary

8

primary lymphoid follicles

contain follicular dendritic cells (FDCs)
-present antigen, but not like other APCs

naive B cells interact with the FDCs to be activated

9

competition for survival signals?

not enough FDCs to activate all B cells - those not activated will die

10

naive B cells express what?

L selectin
CCR-7
LFA1
CXCR4

**allow for B cell homing

these surface molecules activate integrins

11

L selectin

on naive B cells
binds Pnad (Peripheral node addressin)

12

CCR7

on naive B cells
binds CXCL19 or CXCL21

13

LFA1

on naive B cells
binds ICAM-1

14

CXCR4

on naive B cells
binds CXC12

15

CXCL13

secreted by FDCs

mediate the follicle migration of naive B cells

16

What two signals does B cell activation require?

antigen recognition by membrane Ig
-must have repeating epitopes

17

first signal for B cell activation

antigen recognition by membrane IgG
-must crosslink 2 or more BCRs

signaling occurs through Ig alpha and beta tails

18

another way B cells can get first signal?

through the B cell co-receptor
pathogen bound with C3d
-binds CR2

-CR2 and CD19 cytoplasmic

results in a 1000x more intense signal

19

BCR co-receptor complex

CD19
CD81
CR2
lg-alpha and Ig-beta

**does not require the crosslinking of membrane bound Ig to initiate response

20

activated B cells what to alter chemokine receptors?

activated in the primary follicle area
downregulate CXCR5 and increase CCR7
-can leave the follicle and go to para-cortex

21

activated T cells what to alter chemokine receptors?

in the para-cortex/cortex area
down-regulate CCR7 and increase CXCR5

allows B and T cells to meet and interact

22

second signal of B cell activation

two critical ligand pairs
-B7/CD28
-CD40/CD40L

23

B7

upregulated by stimulation of B cell
-can bind to CD28 on T cells

**first signal of T cell was the TCR MHC class II interaction

allows T cells to perform effector function

24

activation of T cell results in what?

increase in expression of CD40L

can interact with CD40 on B cell

provudes signal 2 for the B cell

25

Important concept for B and T cell interaction

CD40L ( T cells) and B7 (B cells) are dependent on antigen stimulation

only lymphocytes specifically interacting with antigen will be activates

**maintains specificity

26

CD40 expression on B cell?

constitutively expressed

27

Class switching in the germinal center

cytokines from T cells provide the switch for this

IL-4 = IgE
IFN-gamma = IgG2a
TGF-beta and IL-5 = IgA


second function is B cell proliferation

28

cytokine that stimulates IgE production?

IL-4

29

cytokine that stimulates IgG2a production?

IFN-gamma

30

cytokine that stimulates IgA production?

TGF-beta and IL-5

31

what signaling triggers isotype switching?

CD40:C40L and cytokines

increase the accessibility of the DNA at specific C regions

rearrange VDJ gene segment recombines with a downstream C region (intervening DNA deleted)

32

T-dependent antigens?

peptides (proteins only)

33

activation-induced deaminase?

key enzyme in isotype switching
-expressed in response to CD40 signaling

34

Ig in naive B cells

IgM and IgD

35

Ig in naive B cell with LPS

no class switching occurs

36

Ig in naive B cell with LPS and IL-4

switching at gamma and epsilon

**keep in mind, will only produce one C region

37

Ig in naive B cell with LPS and TGF-beta

switching at gamma and alpha

**keep in mind, will only produce one C region

38

affinity maturation

aka somatic hypermutation

under activity of AID
-converts Cs to Us

introduces point mutations into V regions of gene

39

what is required for affinity maturation?

CD40/CD40L

T-dependent antigen required

40

what happens to the selected B cells?

move back to the germinal center
-B cell now has higher affinity

interacts with FDCs and TfH cells

**only the cells with high affinity antigen receptors are selected to survive

41

TfH

T follicular helper cells

42

do T cell receptors undergo affinity maturation?

NO!

43

over time what happens to the number of somatic mutations?

increases toward end of primary response and with every subsequent exposure (secondary and tertiary response)

44

Plasma Cells

terminally differentiated antibody secreting B cells

lose CD19 and 20 expression

identified by CD27**

high secretion rate (hundreds to thousands per second)

survive for long periods of time and capable of mounting the secondary response

45

CD27

marker for plasma B cells

46

T dependent antigens

require T cell help (contact dependent)

proteins

specific for the epitope

47

T independent antigens

don't require T cell help

bacterial cell wall like LPS activation

no memory

48

feedback of B cell response?

**IgG binds the IgG receptor and inhibits antibody production

by binding the Ig-alpha and Ig-beta dimers

49

natural antibodies?

IgM

produced by B-1 and margin zone B cells

specific for bacteria in area

cross react with blood alloantigens