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Host and Defense > B Cell-Mediated Immunity > Flashcards

B Cell-Mediated Immunity Flashcards

1
Q

where do B cells under go negative selection?

A

in the bone marrow

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2
Q

where do B cells under go positive selection?

A

secondary lymphoid tissues

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3
Q

where are B cells activated?

A

in the peripheral lymphoid tissues (secondary LT)

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4
Q

what are the two types of effector B cells?

A

memory and plasma cell

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5
Q

once a B cell is a plasma cell can it revert back to a B cell?

A

NO!!!!j

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6
Q

what chemokine attracts B cells to the primary follicle?

A

CXCL 13

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7
Q

what chemokine attract B B cells to the HEV?

A

CCL 21 and CCL19

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8
Q

where do B cells interact with FDCs?

A

in the primary follicle

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9
Q

what cells present antigen to B cells?

A

macs and FDCs

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10
Q

what does B cell activation drive?

A

clonal expansion
class switching
SMH

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11
Q

what are follicular dendritic cells?

A

stromal cells involved in B cell development and activation

  • accumulate antigens via complement receptors
  • NO phagocytic activity NOT a classical DC
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12
Q

what is the receptor for bound complement to antigen on macs and FDCs

A

CR2

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13
Q

what are the three signals for B cell activation?

A

antibody crosslinking
co-receptor signaling
cytokines

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14
Q

what two signals are requisite for B cell activation?

A

antibody crosslinking
co-receptor signaling
*without it the B cell becomes anergic

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15
Q

what does antibody crosslinking do?

A

activates

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16
Q

what does co-receptor signaling do?

A

survival and proliferation

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17
Q

what are the two types of antigens a B cell can be activated by?

A

thymus dependent

thymus independent

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18
Q

thymus dependent antigens

A

protein
protein-assosicated antigen
Tfh cell interaction required
expressed via MHC II

19
Q

thymus independnt antigens

A

PRR-detected (TLRs)
compliment bound antigen
lipids, carbs, toxins

20
Q

Signal 1: antibody crosslinking

A

clustering and aggregation
Ig alpha and beta signaling
*does not tell B cell if the antigen is self or not, it just activates

21
Q

Signal 2: B cell co-receptor signaling

A 
**ensures target is pathogenic**
prevents angery
foreign or self antigen
clonal expansion
1. B cell co-receptor complex (binds to complement)
2. PRRs
3. CD40
22
Q

Signal 3: cytokine signaling

A

Tfh are most common source of cytokines, but local cytokines can provide signals if T cells are gone

23
Q

four roles of cytokine signaling

A

survival and proliferation
class switching
SMH
differentiation

24
Q

what is a cognate pair?

A

when activated B and Tfh cells come together at the follicle boundary
*B cell is presenting the antigen via MHC II

25
Q

how to Tfh cells aid in B cell activation

A

CD40 induces survival and proliferation (co-receptor signal)

  • release cytokines
  • induces differentiation and isotype switching
26
Q

where do cognate pairs go first and what happens there?

A
  • primary focus
  • here the plasma cells just produce IgM to prevent systemic infection
  • *no class-swithing or somatic hympermutation
27
Q

After the cognate pair leaves the primary focus where do they go?

A

the secondary focus, which forms the germinal center

28
Q

what happens at the secondary focus?

A

enormous proliferation to produce plasma and memory cells

  • class switching and SMH
  • selection of most specific plasma cells
29
Q

what is a centroblast?

A

come after the congate pair gets to germinal center

  • proliferating source of new B cells
  • NO Igs on surface
  • SMH
  • class switching
  • create centrocytes
30
Q

what is a centrocyte

A

divide slowly

  • express surface Ig
  • cannot class switch or SMH
  • interact and selected for by FDCs
  • programmed to die
31
Q

what is class switching

A

RAG proteins reactivated in centroblast
change heavy chain
cytokine induced
classes dictate effector function

32
Q

what is somatic hypermutation

A 
directed hypervariable region mutation
single nucleotide insertions and subs
produces new epitope binding region
as centroblasts divide a mutation is introduced
increases Ab affinity 
paired with selection process
33
Q

what cell selects for high-affinity centrocytes?

A

FDCs,

*the Abs are required to compete to get the highest affinity Abs produced

34
Q

what happens to FDC-bound centrocytes?

A

Tfh cells bind and give survival signal and further proliferation
-differentiation into plasma and memory B cells

35
Q

what are the four broad effector functions for antibodies

A

neutralization
opsonization
complement fixation
Antibody-Dependent Cell-mediated cytotoxicity (ADCC)

36
Q

why are Fc receptors important?

A

allow adaptive specificity to innate cells by binding to the antigen bound antibody

37
Q

what are the functions of Fc receptors?

A 
stimulate and inhibitor function
-cytokine production/release
-phagocytosis
-degranulation
-targeted killing
involved in Ig transport
IgG, IgE, IgA
38
Q

what receptor transports IgG across membranes

A

FcRn

39
Q

what is poly-Ig receptor?

A

binds the the Fc portion of the dimeric IgA to transport to mucosal surfaces

40
Q

what Igs generally neutralize?

A

IgA and IgG

41
Q

what cells clear agglutinized antigens?

A

erythrocytes
-they bind complement on antigens that are bound by Abs and deliver them to Macs which have Fc receptors and allow the agglutinized antigen to be killed

42
Q

what are IgEs

A

cell surface receptors for mast, basophils, eosinophils

  • targeted degranulation
  • important in allergies
43
Q

which two Abs initiate complement?

A

IgG and IgM

44
Q

Antibodies provide passive immunity during development how?

A

IgG during gestation
IgA from breast milk
mother’s immunity passed to child

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