L06

Question 1

when are B cells activated

Answer 1

when they bind an AG

Question 2

what do activated B cells give rise to

Answer 2

Plasma cells and memory cells

Question 3

what are the ways in which Ab work

Answer 3

neutralization, opsonization, compliment activation

Question 4

what BCRs are always present in naive B cells

Answer 4

IgM and IgD

Question 5

what provides signal 1 in BCR

Answer 5

Binding of Ag to BCR

Question 6

what BCR-associated polypeptides involved in signal

Answer 6

Igα and Igβ

Question 7

what is the role of compliment molecules in relation to signal one in B cells

Answer 7

they enhance it

Question 8

what compliment molecule is involved in signal 1 of B cell

Answer 8

CR2

Question 9

what are the types of antigens involved in B cell signal 2

Answer 9

T (thymus)-independent Ag (TI)

T (thymus)-dependent Ag (TD)

Question 10

what is signal 2 provided by in T (thymus)-independent Ag (TI):

Answer 10

a) antigen itself or
b) extensive cross-linking of BCR

Question 11

what is signal 2 provided by in T (thymus)-dependent Ag (TD)

Answer 11

CD4+ T cells

Question 12

what class of Ab thro thymus independent signaling

Answer 12

IgM

Question 13

what type of signaling allows Ab class switching

Answer 13

thymus dependent (TI)

Question 14

give an example of a danger signal on dendritic cells

Answer 14

LPS

Question 15

what do TI-1 Ag do

Answer 15

bind to other receptors on all B cells providing signal 2

Question 16

give an example of TI-1 Ag

Answer 16

lipopolysaccharide from Gram -ve bacteria binds to TLR4 expressed by B cells

Question 17

what are the types of thymus independent TI ag

Answer 17

TI-1

TI-2

Question 18

what are the features of TI-2 Ag

Answer 18

contain repeated epitopes

will therefore cross-link many BCR molecules on same B cell surface

take longer (more Ag required) to induce B cell activation

Antibody responses to TI-2 Ag typically don’t develop until > 5 yrs. in humans

Question 19

what are the features of the repeated epitopes in TI-2 Ag

Answer 19

often polysaccharides (same sugar repeated lots)

important in some bacterial infections (coated)

Question 20

where does signal 2 in B cells come from

Answer 20

CD40
cytokines secreted by T cells

Question 21

what plays a role in class switching of Ab

Answer 21

cytokines secreted by the T cells

Question 22

what are the examples of a conjugate vaccine

Answer 22

Haemophilus influenzae type b when the protein tetanus toxoid is coupled

MenC

peneumococcal conjugate vaccine

Question 23

what does the CD4 T cell do after binding to an MHC 2

Answer 23

expresses CD40 ligand (CD40)

secretes cytokines

Question 24

what does CD40/CD40L binding do

Answer 24

sends signal 2 to B cell to proliferate

induces activation induced deaminase (AID)

Question 25

what does activation induced deaminase (AID) do

Answer 25

required for class switching and somatic hypermutation

Question 26

where in secondary lymphoid do B cells divide rapidly

Answer 26

form germinal centres (GC)

Question 27

what do B cells that divide rapidly undergo

Answer 27

somatic hypermutation of Ig genes isotype switching

Question 28

what is the germinal centres (GC) within a B cell follicle formed of

Answer 28

conjugates of B lymphoblasts and T cells

Question 29

B cells divide rapidly to form _______

Answer 29

centroblats

Question 30

What other types of cells present in B cell germinal centre

Answer 30

Follicular dendritic cells, T cells

Question 31

What is the role of T cells in the B cells germinal centre

Answer 31

Binds to B cells = signal 2

Question 32

What type of T cell is present in the GC?

Answer 32

TFH

Question 33

What is the role of TFH

Answer 33

continuous signal 2 in B cells

Question 34

What cytokine is involved to allow the movement of T cells into GC?

Answer 34

IL6

Question 35

What are the three fates of B cells once in the GC

Answer 35

1. Differentiate into plasma cells 2. form long lived memory cells 3. die within lymphoid tissue

Question 36

What does a B cell do after they differentiate into plasma cells

Answer 36

- secrete various isotypes - high affinity antibodies

Question 37

When would a B cell die within the lymphoid tissue

Answer 37

BCR ni longer binds antigen (due to unsuccessful v chain or somatic mutation

Question 38

What do somatic hypermutations result in?

Answer 38

Point mutations into V regions, 1,000,000 times higher mutations.

Question 39

What are the enzymes primarily involved in somatic hypermutations?

Answer 39

AID - activation induced deaminse and DNA repair gene

Question 40

Are follicular dendritic cells bone marrow derived?

Answer 40

No

Question 41

What is the role of the follicular dendritic cells?

Answer 41

APC

Question 42

Describe B cell affinity maturation?

Answer 42

Centrocytes compete with e/o for Ag on FDC&signals from THC, BCR with better affinity will present more efficiently and recieve CD40 signal from TFH cell

Question 43

What happens if B cells fail to develop affinity maturation?

Answer 43

- apoptosis - recycled to the dark zone

Question 44

What sort of cytokines are produced by TFH?

Answer 44

Th1 or Th2

Question 45

What cell produces CD40?

Answer 45

B cell

Question 46

What are the roles of CD40?

Answer 46

- protects centrocytes from apoptosis - induces isotype switching

Question 47

How are different isotypes induced?

Answer 47

Different cytokines

Question 48

Is isotype switching RAD mediated?

Answer 48

No

Question 49

What is the initial BCR Ig class?

Answer 49

IgM

Question 50

What is the role of cytokines in isotype switching?

Answer 50

Informs where to cut the DNA