Lecture 14: B Cell activation and Antibody Production

Question 1

Primary response differs from secondary response how

Answer 1

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

Question 2

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

Answer 2

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

Question 3

Antibody responses to what require CD4+ T cell help

Answer 3

Protein antigens

Question 4

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

Answer 4

Follicular helper B cells

Activated B cells proliferate here

Question 5

Follicular B-2 cells respond to

Answer 5

Protein Ags and thus initiate T-dependent Ab responses

Question 6

Marginal zone B cells respond to

Answer 6

Multivalent Ags and are T independent

Question 7

B-1 cells in mucosal sites respond to

Answer 7

Multivalent Ags and are T independent

Question 8

B-1 B cells arise from where

Answer 8

Fetal liver

Question 9

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

Answer 9

CXCL13 chemokine secrected by resident follicular DCs

It attracts Naïve B cells to follicules

Question 10

Soluble Ag fate in delivery to LN

Answer 10

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

Question 11

Large Ag fate in delivery to LN

Answer 11

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

Question 12

Microbe/Ag-Ab complex fate in delivery to LN

Answer 12

Captured by subcapsular sinus macrophages which deliver Ags to follicles

Question 13

FDCs have unique capacity to retain

Answer 13

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

Question 14

Ag retention by FDCs is mediated by

Answer 14

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

Question 15

Follicular B cell survival depends on

Answer 15

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

Question 16

BAFF is produced by

Answer 16

Myeloid cells in lymphoid follicles and bone marrow

Question 17

T or F: FDCs express class II MHC

Answer 17

False

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

Question 18

B-T cell interaction leads to

Answer 18

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

Question 19

Generation of Tfh cells requires

Answer 19

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

Question 20

Tfh cells are drawn into lymphoid follicles by

Answer 20

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

Question 21

Tfh cells express

Answer 21

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

Question 22

IL-21 importance in GC

Answer 22

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

Question 23

What happens in the dark zone of GC

Answer 23

Activated B cells migrate into area and proliferate.

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

Question 24

What happens in the light zone

Answer 24

B cells encounter follicular DCs displaying Ag and Tfh cells

Question 25

Ab secreting cells go where, memory B cells go where

Answer 25

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

Question 26

Mantle zone

Answer 26

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

Question 27

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

Answer 27

CCR7

Question 28

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

Answer 28

True

Question 29

MZ B cells respond to

Answer 29

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

Question 30

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

Answer 30

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

Question 31

This T cell independent pathway that MZ B cells use requires

Answer 31

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

Question 32

The Ags presented to MZ B cells are generally in

Answer 32

Native conformation, not processed by APCs

Question 33

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

Answer 33

Bind CR@ complement receptor

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

Question 34

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

Answer 34

Plasmacytoid DCs

Question 35

Polysaccharide Ags in spleen captured by who

Answer 35

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

Question 36

Ag presenting MZ macrophages stimulate MZ B cells via

Answer 36

BCR and TLRs

Question 37

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

Answer 37

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