2.7

Question 1

Activation of B Lymphocytes and Production of Antibodies

outcome (4)

Answer 1

ab secretion
isotype switching
affinity maturation
memory b cell

Question 2

t-dependent

Answer 2

isotype switched, high affinity ab; memory b cells, long lived plasma cells

Question 3

t-independent

Answer 3

mainly IgM, low affinity ab; short lived plasma cells

Question 4

reponse: primary
lag after immunization:
peak response: 
ab isotype: 
ab affinity:

Answer 4

5-10 days
smaller
IgM>IgG
lower average affinity, more variable

Question 5

reponse: secondary 
lay after immunization:
peak response: 
ab isotype: 
ab affinity:

Answer 5

1-3 days
larger
relative increase in IgG and under certain situations, in IgA or IgE (heavy chain isotype switching)
higher average affinity (affinity maturation)

Question 6

Receptor clustering needed:
– or more receptors bound
to antigens

Answer 6

2

Question 7

Figure 7-4. Antigen receptor-mediated signal transduction in B lymphocytes (5)

Answer 7

cross linking of membrane Ig by antigen
tyrosine phosphorylation events 
biochemical intermediates 
active enzymes 
TF (myc, NFAT, NF beta, AP-1)

Question 8

Figure 7-5. Role of innate immune signals
in B cell activation.
(A) complement receptor (CR2) binding by
— bound to microbe.
(B) (B) Toll-like receptor (TLR) binding by
—

Answer 8

3Cd

PAMP

Question 9

c3a:

Answer 9

inflammation

Question 10

c3b

Answer 10

opsonization and phagocytosis

Question 11

c5a

Answer 11

inflammation

Question 12

c6-9

Answer 12

lysis of microbe

Question 13

antigen binding to and cross linking of membrane Ig
changes in activated B cells
functional consequences (5)

Answer 13

increased survival, proliferation
interaction with helper t cells 
responsiveness to cytokines
migration from follicle to t cell zone 
ab secretion

Question 14

Figure 7-8. Antigen presentation by B lymphocytes to helper T cells (4)

Answer 14

b cell recognition of naive protein antigen
receptor mediated endocytosis of antigen
antigen processing and presenation
t cell recognition of antigen

Question 15

Activated T cells that recognize antigen presented on B cells use — ligand
and cytokines to activate the B cell

Answer 15

CD40

activated helper t cell expressed CD40L, secretes cytokines
b cells are activated by CD40 engagment, cytokines
b cell proliferation and differentiation

Question 16

Figure 7-10. The germinal center reaction (4)

Answer 16

activation of b cells and migration into germinal center
b cell proliferation
somatic mutation and affinity maturation; isotype switching
exit of high affinity ab secreting cells and memory b cells

Question 17

IgM

principal effector functions

Answer 17

complement activation

Question 18

IgG subclasses

principal effector functions

Answer 18

Fc receptor dependent phagocyte responses, complement activation, neonatal immunity (placental transfer)

Question 19

IgE

principal effector functions

Answer 19

immunity against helminths

mast cell degranulation (immendiate hypersensitivity)

Question 20

IgA

principal effector functions

Answer 20

mucosal immunity (transport of IgA through epithelia)

Question 21

“Switch recombination”

Answer 21

Previously formed VDJ exon recombines
to become adjacent to a different
constant region gene (than µ; IgM)

Question 22

S =

Answer 22

switch regions

Question 23

AID =

Answer 23

activation-induced deaminase;
alters nucleotides so they can be cleaved
by other enzymes, allowing S regions to
be brought together

Question 24

Figure 7-12. Mechanism of immunoglobulin heavy-chain isotype switching (4)

Answer 24

INDUCTION OF AID
recombination of Su with Sgamma, deletion of intervening C genes
transcription; rna splicing
translation

Question 25

Repeated exposure to a protein antigen drives creation of

Answer 25

higher affinity antibodies

Question 26

Somatic Hypermutation | AID =

Answer 26

``` activation-induced deaminase is involved; deaminates cytosine (DNA base) to uracil. Sometimes uracil is cleaved (see isotype switching) and repaired by an error-prone mechanism. Even when uracil persists, it results in a base pairing change. ```

Question 27

FDCs

Answer 27

``` present antigen via antibodies bound to Fc receptors or complement receptors instead of MHC molecules Antigens are never internalized by FDCs. (figure does not depict a surface bound antibody on FDC). The antibodies are those that were secreted by B cells themselve ```

Question 28

Figure 7-14. Selection of high-affinity B cells in germinal centers (4)

Answer 28

b cell activation by protein antigen and helper t cells b cells with somatically mutated Og V genes and Igs with varying affinities for antigen b cells with high affinity membrane Ig bind antigen on FDC and present antigen to helper t cell b cells that recognize antigen and FDCs or interact with hylper t cells are selected to survive; other b cells die

Question 29

chemical nature thymus dependent antigen: thymus independent antigen:

Answer 29

proteins | polymeric antigens, especially ploysaccharides; also glycolipids, nucleic acids

Question 30

``` features of ab response: IgM, G, E, A isotype switching: affinity maturation: plasma cells: secondary response (memory b cells): ```

Answer 30

yes yes long lived yes

Question 31

isotype switching: IgM, IgG affinity maturation: plasma cells: secondary response (memory b cells):

Answer 31

low levels of switching to IgG little or no short lived only seen with some polysaccharide antigens

Question 32

Regulation of the humoral response: antibody feedback (4)

Answer 32

secreted ab forms complex with antigen antigen ab complex binds to b cell iG and receptor inhibition of B cell response block in B cell receptor signaling

Question 33

Humoral response terminated | once

Answer 33

sufficient quantities of IgG are produced to result in this combination of binding on a B cell