B Cell Immunity

Question 1

What are the three different kinds of B cells?

Answer 1

B1, conventional B2, marginal B3 (MZ)

Question 2

What is the V-region repertoire of B1 cells?

Answer 2

Restricted

Question 3

What are the primary locations of the three kinds of B cells

Answer 3

B1: body cavities (peritoneal, pleural)

B2: secondary lymphoid organs

B3: spleen

Question 4

Which of the B cell populations does not need T cell help?

Answer 4

B1 - They respond to carbohydrate Ag, which doesn’t require T cell help

Question 5

Which of the B cell populations has no memory?

Answer 5

B1

Question 6

Which B cells are produced in the fetal liver?

Answer 6

B1

Question 7

What is the mode of renewal of the different B cells?

Answer 7

B1: Self renewing

B2: replaced from bone marrow

B3: Long lived

Question 8

Do B1 cells undergo somatic hypermutation or isotype switching?

Answer 8

No!

Question 9

Where are B3 cells found?

Answer 9

Marginal zone of the spleen: at the junction of the white and red pulp - the interface of circulation of lymphoid tissue

Question 10

Do B3 cells require T cell help?

Answer 10

Sometimes…

Question 11

What cells are innate-like?

Answer 11

B1 and B3

Question 12

What are most adaptive immune responses mediated by?

Answer 12

B2

Question 13

Rank the route of immunization by immunogenic response

Answer 13

subcutaneous > intraperitoneal > intravenous or intragastric

Question 14

what do adjuvants do?

Answer 14

typically delays antigen release and makes particulate immunogen readily ingestible by APCs

makes Ag particulate and large enough to stimulate a response

Question 15

What dose of immunogen will result in increased immunogenicity?

Answer 15

Intermediate amount - both low and high doses will not give the same response

Question 16

How does size affect the immunogenicity?

Answer 16

the larger the Ag, the more immunogenic

Question 17

What are the two signals B cells require to be activated?

Answer 17

T-dependent:

1. interaction of B cell with Ag and
2. interaction of TCR with peptide/MHC complex and interaction with co-stimulatory molecules CD40 (B cell) and CD40L (T cell)

T-independent: For T-independent Ag, such as polysaccharide, the second signal can be provided by the Ag (no T cell is needed)

Question 18

What do activated Th cells secrete/express to stimulate B cell proliferation?

Answer 18

Interaction of TCR with Ag/MHC triggers the Th cell to secrete cytokines IL4, IL5, IL6 and to express CD40L

Question 19

B and T cells can recognize the same Ag. What is different about what they recognize?

Answer 19

They recognize the same Ag, but not the same epitope

Question 20

What is different about primary vs secondary Ab response in regards to speed and Ig produced?

Answer 20

Primary is slow and primarily IgM

Secondary is fast and is primarily IgG

Question 21

What will increase at the end of the primary response?

Answer 21

affinity, due to somatic hypermutation, and Ab titer

Question 22

What are the major Igs of the secondary immune response?

Answer 22

IgG, and to a lesser extent IgE and IgA

Question 23

When does isotype switching occur and what is it regulated by?

Answer 23

during T-dependent response, regulated by T-cell cytokines

Question 24

What gene is rearranged by isotype switching

Answer 24

C heavy

Question 25

What enzyme is required for switch recombination?

Answer 25

AID

Question 26

What does AID recognize to mediate switch recombination?

Answer 26

switch sites upstream of the different Ig genes (except for delta)

Question 27

What are three types of differentiation that occur in germinal centers?

Answer 27

isotype switching, somatic hypermutation of Ig genes, development of memory B cells/plasmablasts

Question 28

What happens after an activated B cell presents Ag to a helper T cell?

Answer 28

somatic hypermutation in Ig V regions in rapidly proliferating germinal center B cells

Question 29

What happens if a mutated B cell develops low affinity surface Ig?

Answer 29

It will be unable to cross link receptors and will die by apoptosis

Question 30

What happens if a mutated B cell develops high affinity surface Ig?

Answer 30

BCR and Thelper cross linking sustain B cell maturation and proliferation, and the B cell can develop into a memory B cell or a plasmablast

Question 31

What happens if a patient has an AID deficiency?

Answer 31

Only has IgM and the Ig genes are not somatically diversified

Question 32

What is the maturation, differentiation, and isotype switching dependent upon?

Answer 32

Thelper cells

Question 33

Discuss how Thelper cells enhance B cell function

Answer 33

APC presents Ag via MHCII to Thelper cell which becomes activated The TCR then recognizes Ag/MHCII on the B cell and the Thelper secretes cytokines which stimulates proliferation and differentiation

Question 34

What are the differences in Ig produced by B cells stimulated by T-independent Ag?

Answer 34

Ab produced is generally IgM and they are not somatically mutated, and are thus lower affinity

Question 35

List some T-independent Ag

Answer 35

``` bacterial lipopolysaccharide polymerized flagellin pneumococcal polysaccharide natural polysaccharide dextrans levans hyaluronic acid ```

Question 36

do T-independent Ags result in the formation of B memory cells?

Answer 36

No