Lecture 14: B Cell activation and Antibody Production Flashcards

1
Q

Primary response differs from secondary response how

A
Secondary is -
More rapid
Larger amounts of Abs produced
Isotype switching of heavy chain occurs
Affinity maturation occurs
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2
Q

Antibody responses to what do not require Ag-specific helper T lymphocytes

A

Multivalent non-protein Ags with repeating epitopes, such as polysaccharides, some lipids, and nucleic acids

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3
Q

Antibody responses to what require CD4+ T cell help

A

Protein antigens

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4
Q

What facilitates the formation of germinal centers, and what happens in these centers

A

Follicular helper B cells

Activated B cells proliferate here

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5
Q

Follicular B-2 cells respond to

A

Protein Ags and thus initiate T-dependent Ab responses

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6
Q

Marginal zone B cells respond to

A

Multivalent Ags and are T independent

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7
Q

B-1 cells in mucosal sites respond to

A

Multivalent Ags and are T independent

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8
Q

B-1 B cells arise from where

A

Fetal liver

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9
Q

What guides the movement of Follicular B cells into the follicles of secondary lymph organs

A

CXCL13 chemokine secrected by resident follicular DCs

It attracts Naïve B cells to follicules

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10
Q

Soluble Ag fate in delivery to LN

A

Small Ags (Smaller than 70kD generally) may reach B cell zone of the follicle and interact directly with specific B cells

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11
Q

Large Ag fate in delivery to LN

A

May be captured by resident FDCs and transported into follicles where they can activate B cells

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12
Q

Microbe/Ag-Ab complex fate in delivery to LN

A

Captured by subcapsular sinus macrophages which deliver Ags to follicles

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13
Q

FDCs have unique capacity to retain

A

Immune Ag-Ab complexes on their surface for long periods (weeks to months)

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14
Q

Ag retention by FDCs is mediated by

A

FcyRIIB Fc receptors or CR1/CR2 (CD21) complement receptors

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15
Q

Follicular B cell survival depends on

A

Signals from BCR as well as inputs received from cytokine BAFF (B cell activating factor of the TNF family)

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16
Q

BAFF is produced by

A

Myeloid cells in lymphoid follicles and bone marrow

17
Q

T or F: FDCs express class II MHC

A

False

And they do not phagocytose/process exogenous Ags for Class II MHC

18
Q

B-T cell interaction leads to

A

Minimal isotype switching, and generation of short lived plasma cells mainly producing IgM

  • B cells then migrate to germinal centers and undergo :
  • somatic mutation
  • affinity maturation
  • isotype switching
  • generation of memory B cell and long lived plasma cells
19
Q

Generation of Tfh cells requires

A

Sequential activation of T cells, first by DCs and then by B cells. The Tfh cells then migrate to GCs where they activate B cells

20
Q

Tfh cells are drawn into lymphoid follicles by

A

CSCL13, they play a critical role in GC formation and function

21
Q

Tfh cells express

A

ICOS, PD-1, IL-21 and Bcl-6

22
Q

IL-21 importance in GC

A

Important in GC for development of B cells, isotype switching, affinity maturation and antibody production

23
Q

What happens in the dark zone of GC

A

Activated B cells migrate into area and proliferate.

They undergo extensive isotype switching and somatic hypermutation of Ig V genes here

24
Q

What happens in the light zone

A

B cells encounter follicular DCs displaying Ag and Tfh cells

25
Q

Ab secreting cells go where, memory B cells go where

A

Ab secreting cells reside in bone marrow as long lived plasma cells
Memory B cells enter the recirculating lymphocyte pool

26
Q

Mantle zone

A

Surrounds GC and contains tightly packed small B cells of the primary follicles, pushed aside by GCs

27
Q

The expression of what induces migration of B cells toward the T cell zone

A

CCR7

28
Q

T or F: Marginal zone B cells mount rapid Ab responses to both T cell dependent and T c ell independent antigens

A

True

29
Q

MZ B cells respond to

A

Blood borne viruses and encapsulated bacteria by using ‘crossover’ defensive strategies

30
Q

MZ B cell activation threshold compared to follicular B cells– this permits what

A

MZ B cells have lower activation threshold, which permits rapid initiation of IgM production and of IgG/IgA class switch recombination in the absence of CD40 dependent help from Tfh cells

31
Q

This T cell independent pathway that MZ B cells use requires

A

Dual BCR and TLR engagement by conserved microbial Ags together with co-stimulatory signals from DCs and macrophages via various cytokines

32
Q

The Ags presented to MZ B cells are generally in

A

Native conformation, not processed by APCs

33
Q

Ags in immune complexes may bind what on MZ B cell, who then do what

A

Bind CR@ complement receptor

MZ B cells can then transfer the immune complexe-containing Ags to follicular DCs

34
Q

Blood borne pathogens are captured by what for transfer to the spleen

A

Plasmacytoid DCs

35
Q

Polysaccharide Ags in spleen captured by who

A

MZ macrophages and are then displayed or transferred to MZ B cells in area

36
Q

Ag presenting MZ macrophages stimulate MZ B cells via

A

BCR and TLRs

37
Q

Stimulation of MZ B cells by MZ macrophages delivers signal that causes

A

CSR and Ab production, after ligating BAFF and APRIL (a proliferation inducing ligand) - which are released by APCs in response to microbial TLR ligands