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Host Defense > Lecture 10: B Cell Immunity > Flashcards

Lecture 10: B Cell Immunity Flashcards

1
Q

What are the 3 kinds of B cells?

A

1) B-1
2) B-2
3) MZ (marginal zone)

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2
Q

Most adaptive responses are mediated by _____. (the other 2 types are innate-like)

A

B-2

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3
Q

Where are MZ cells located?

A

spleen

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4
Q

Where are B-1 cells located?

A

body cavities (peritoneal, pleural)

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5
Q

What are the only B cells that have memory?

A

B-2

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6
Q

Why is snake venom so lethal?

A

because it is usually delivered at such inconsequential doses that it goes undetected by adaptive immune system

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7
Q

____ mediates the primary response while ____ mediates the secondary response

A

IgM; IgG

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8
Q

True or false: the larger the antigen, the more immunogenic it is

A

True

so since insulin is so small, doctors were able to get away with giving small doses of porcine insulin

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9
Q

What is the site of greatest immunogenicity of injection?

A

subcutaneous > intraperitoneal > intravenous > intragastric

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10
Q

What are adjuvants and what is a common one used in human vaccines?

A

make antigens insoluble to elicit a larger, more potent immune response

Alum

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11
Q

How does Alum work to increase immunogenicity?

A

delays release of antigen; enhances macrophage uptake

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12
Q

True or False: Most B cell responses require T cell help for activation?

A

TRUE

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13
Q

How do B cells recruit T cells?

A

BCRs interact with antigen –> antigen is internalized with BCR and degraded. Peptides associate with MHC-II and go to surface of B cell. TCR on T cell recognizes peptide in context of MHC-II and is stimulated to produce cytokines which activate B cell to proliferate into Ab-producing cells

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14
Q

What 3 signals are required for activation of B cell?

A

1) interaction of BCR with antigen
2) interaction of TCR with peptide/MHC-II
3) ineraction between costimulatory molecules CD40 (B cell) and CD40L (T cell)

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15
Q

T independent antigens are usually __________

A

polysaccharides

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16
Q

Once a B cell interacts with a T cell, the T cell secretes B cell stimulatory cytokines like _____, ______, and _____ as well as expresses _______.

A

IL-4
IL-5
IL-6
CD40L

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17
Q

True or False: B and T cells must recognize the same antigen

A

TRUE (but not the same epitope)

B cells recognize native epitope
T cells recognize peptide ALWAYS in the context of MHC

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18
Q

How do you immunize babies against carb antigens if those are T-independent responses?

A

trick immune system to exploit babies’ ability to make a T-dependent response (which responds to proteins)

attach carb from flu to tetanus toxin

19
Q

How do you immunize babies against carb antigens if those are T-independent responses?

A

trick immune system to exploit babies’ ability to make a T-dependent response (which responds to proteins)

attach carb from flu to tetanus toxin

20
Q

Primary response is ______ (IgM)

Secondary response is ______ (IgG)

A

slow

fast

21
Q

Why does affinity increase so much after primary response?

A

somatic hypermutation and higher antibody titer

22
Q

Are lipids or nucleic acids immunogenic?

A

NO

23
Q

Isotype switching occurs by rearrangement of the ____ gene

A

CH

24
Q

When does isotype switching occur?

A

during T-dependent responses (regulated by T-cell cytokines)

25
Q

What enzyme is required for somatic rearrangement?

A

AID (activation induced cytidine deaminase)

26
Q

What are switch sites?

A

upstream repeat sequences with high degree of similarity between different switch regions

27
Q

While VDJ rearrangement is mediated by _____ and __________, isotype switching is mediated by _____

A

RSS and RAG1/RAG2

AID

28
Q

Where does isotype switching occur?

A

germinal center

29
Q

Where do VDJ rearrangements occur?

A

bone marrow and thymus

30
Q

What 3 things happen in the germinal centers?

A

1) somatic hypermutation
2) class switch recombination
3) development of memory B cells

31
Q

What happens in the dark zone of germinal centers?

A

hypermutation

32
Q

What happens in the light zone?

A

selection of B cells that have highest affinity

33
Q

AID deficient patients have ONLY _____ (what antibody)

A

IgM

34
Q

What happens in germainl centers?

A

class switch, memory selection, plasma cell development

35
Q

How are the cells with highest affinity receptors selected in the germinal centers?

A

antigen in the form of antigen-antibody complexes are bound to follicular dendritic cells followed by B cell presentation of antigen to th cells

36
Q

Cells leave germinal centers as either _________ or _________

A

memory cells or plasma cells

37
Q

Cells leave germinal centers as either _________ or _________

A

memory cells or plasma cells

38
Q

How are Th cells activated?

A

1) APC takes up antigen, processes it and expresses peptides in context of MHC II
2) TCR recognizes peptide/MHC-II complex and becomes activated

39
Q

How are Th cells activated?

A

1) APC takes up antigen, processes it and expresses peptides in context of MHC II
2) TCR recognizes peptide/MHC-II complex and becomes activated

40
Q

Activated B cells come from ___________ + ___________

A

activated Th cells and antigen-specific B cells

41
Q

What are the only antigens that can signal B cells to produce antibody?

A

TI-2

42
Q

What is the antibody response to TI antigen (polysaccharide)

A
  • no germinal center formation
  • no somatic hypermutation
  • no memory
  • no isotype switch
43
Q

What are the 3 methods by which antibodies mediate humoral immunity?

A

1) neutralization (antibody prevents bacterial adherence)
2) opsonization (antibody promotes phagocytosis)
3) Complement

44
Q

Activation through Fc-receptors requires Ig to be ___________ (free/aggregated)

A

aggregated (allows cross-linking of Fc receptors)

Host Defense (21 decks)

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