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Host Defense Exam 2 > B Cell Immunity > Flashcards

B Cell Immunity Flashcards

1
Q

What are the three different kinds of B cells?

A

B1, conventional B2, marginal B3 (MZ)

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2
Q

What is the V-region repertoire of B1 cells?

A

Restricted

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3
Q

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

A

B1: body cavities (peritoneal, pleural)

B2: secondary lymphoid organs

B3: spleen

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4
Q

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

A

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

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5
Q

Which of the B cell populations has no memory?

A

B1

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6
Q

Which B cells are produced in the fetal liver?

A

B1

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7
Q

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

A

B1: Self renewing

B2: replaced from bone marrow

B3: Long lived

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8
Q

Do B1 cells undergo somatic hypermutation or isotype switching?

A

No!

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9
Q

Where are B3 cells found?

A

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

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10
Q

Do B3 cells require T cell help?

A

Sometimes…

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11
Q

What cells are innate-like?

A

B1 and B3

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12
Q

What are most adaptive immune responses mediated by?

A

B2

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13
Q

Rank the route of immunization by immunogenic response

A

subcutaneous > intraperitoneal > intravenous or intragastric

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14
Q

what do adjuvants do?

A

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

makes Ag particulate and large enough to stimulate a response

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15
Q

What dose of immunogen will result in increased immunogenicity?

A

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

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16
Q

How does size affect the immunogenicity?

A

the larger the Ag, the more immunogenic

17
Q

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

A

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)

18
Q

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

A

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

19
Q

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

A

They recognize the same Ag, but not the same epitope

20
Q

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

A

Primary is slow and primarily IgM

Secondary is fast and is primarily IgG

21
Q

What will increase at the end of the primary response?

A

affinity, due to somatic hypermutation, and Ab titer

22
Q

What are the major Igs of the secondary immune response?

A

IgG, and to a lesser extent IgE and IgA

23
Q

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

A

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

24
Q

What gene is rearranged by isotype switching

A

C heavy

25
Q

What enzyme is required for switch recombination?

A

AID

26
Q

What does AID recognize to mediate switch recombination?

A

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

27
Q

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

A

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

28
Q

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

A

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

29
Q

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

A

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

30
Q

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

A

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

31
Q

What happens if a patient has an AID deficiency?

A

Only has IgM and the Ig genes are not somatically diversified

32
Q

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

A

Thelper cells

33
Q

Discuss how Thelper cells enhance B cell function

A

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

34
Q

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

A

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

35
Q

List some T-independent Ag

A 
bacterial lipopolysaccharide
polymerized flagellin
pneumococcal polysaccharide
natural polysaccharide
dextrans
levans
hyaluronic acid
36
Q

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

A

No

Host Defense Exam 2 (11 decks)

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