B Cell Activation (Exam 2)

Question 1

What are the 3 phases of the humoral immune response?

Answer 1

1. recognition phase
2. proliferation phase
3. differentiation phase

Question 2

In the recognition phase of humoral immune response, ________ recognize antigen and become activated.

Answer 2

B cells

Question 3

In the proliferation phase of humoral immune response, activated B cells undergo __________.

Answer 3

clonal expansion

Question 4

In the differentiation phase of humoral immune response, progeny B cells develop into effector cells as either _______ or ______.

Answer 4

plasma cells
memory B cells

Question 5

_________ antigen require help of CD4+ T cells for recognition while _______ does can formulate a responses without T cell help.

Answer 5

thymus-dependent
thymus-independent

Question 6

What types of antigen is thymus independent? Dependent?

Answer 6

Independent: polysaccharides, lipid, nucleic acid antigen

Dependent: protein antigen

Question 7

What cell type mediates thymus-dependent antigen?

Answer 7

follicular B cells

Question 8

Thymus-independent antigen is mediated by ________ cells in secondary lymphoid tissue and ________ cells in mucosal sites/peritoneum.

Answer 8

marginal zone B cells
B1 cells

Question 9

What 3 anatomic compartments are humoral immune responses initiated in?

Answer 9

1. spleen
2. lymph nodes
3. mucosal lymphoid tissue

Question 10

What is class switching?

Answer 10

process where activated B cells begin producing antibodies other than IgM (such as IgA, IgG, IgE)

Question 11

Term for process where overtime, B cells produce higher affinity antibodies that are selected for.

Answer 11

affinity maturation

Question 12

Which antibodies are secreted in the primary antibody response vs. secondary antibody response?

Answer 12

primary: IgM
secondary: class-switch antibodies (IgA, IgG, IgE)

Question 13

Which antibody isotypes serve as antigen receptors on the surface of naive B cells?

Answer 13

IgM + IgD

Question 14

What does ITAM stand for?

Answer 14

immunoreceptor tyrosine-based activation motif

Question 15

What does ITAM do?

Answer 15

motif on B cell receptor which helps initiate a signaling cascade to activate the cell

Question 16

ITAM recruits _______ to cause a conformational change which allows for a signaling cascade which activates B cells.

Answer 16

tyrosine kinase

Question 17

What are two invariant molecules? What special structure is associated with them?

Answer 17

Ig(alpha) + Ig
ITAM

Question 18

What do helper T cells help B cells to do?

Answer 18

produce signals to stimulate B cell responses (such as formation into plasma cells and B memory cells)

Question 19

Where do early events in T-cell dependent B cell activation occur?

Answer 19

just outside follicle at extrafollicular locus

Question 20

Within a follicle of a secondary lymphoid organ, _________ is a B cell zone which produces high quality antibodies and B cells undergo proliferation.

Answer 20

germinal center

Question 21

In helper T cell-mediated B cell activation, B cells bind to antigen and become activated. This leads to an upregulation of ________. What is the purpose?

Answer 21

costimulators (B7)
better able to activate T cells

Question 22

What two structures do T cells recognize in T cell-mediated B cell activation and allows them to respond?

Answer 22

MHC-peptide complex + costimulators

Question 23

When T cells recognize MHC-peptide complex and costimulators, they express ______ ligand which stimulates them to secrete _________.

Answer 23

CD40
cytokines

Question 24

CD40 binding to B cells causes what response? Cytokines from T cells stimulate B cells to do what?

Answer 24

CD40 –> B cell proliferation
Cytokines –> germinal center (high quality antibody production)

Question 25

(T/F) The initial interaction between B and CD4 T cells outside of the secondary lymphoid organ follicle can induce some isotype switching.

Answer 25

True

Question 26

Where does most isotype switching occur?

Answer 26

germinal center

Question 27

Term for randomized mutation which leads to B cells with high affinity antibodies which will survive when others will die by apoptosis.

Answer 27

somatic hypermutation

Question 28

What is B7?

Answer 28

costimulatory molecule upregulated in T cell-mediated B cell activated so B cells can better activate T cells

Question 29

_______ is a protein on cell membrane which binds to B cell receptors to stimulate their proliferation and differentiation which leads to a germinal center reaction.

Answer 29

CD40

Question 30

What are the 4 antibody subclasses?

Answer 30

IgG IgA IgM IgE

Question 31

Match the effector functions to the appropriate antibody isotype: 1. helminth immunity | mast cell degranulation 2. mucosal immunity 3. complement activation 4. opsonization, phagocytosis, complement activation, neonatal immunity

Answer 31

1. IgE 2. IgA 3. IgM 4. IgG

Question 32

Each cytokine can influence class switching. Match which antibody isotype is stimulated by each: 1. no cytokine signal 2. IFN-y 3. IL-4 4. TGF-B 5. IL-5

Answer 32

1. IgM 2. IgG2a 3. IgG1; some IgE 4/5. IgA

Question 33

Follicular dendritic cells express high levels of ______ and ______ receptors which bind to complement or antibodies.

Answer 33

Fc complement

Question 34

What is the main function of IgM?

Answer 34

complement activation

Question 35

Explain antibody feedback.

Answer 35

IgG has regulatory or inhibitory role on B cell response to antigen (to keep response in check)

Question 36

________ is an inhibitory receptor on antigen-specific B cell which inhibits B cell activation.

Answer 36

Fc-y RII

Question 37

Fcy RII receptor can inhibit B cell response because it has _______.

Answer 37

ITIM (immunoreceptor tyrosine-based inhibition motif)

Question 38

When Fc-y RII receptor is engaged, it (phosphorylates/dephosphorylates) ITIM which forms a "docking site" called _______ which (phosphorylates/dephosphorylates) to inhibit the signaling pathway, and therefore, B cell activation is inhibited.

Answer 38

phosphorylates SHIP dephosphorylates

Question 39

How does the circulating level of secreted IgM and IgG modulate the antibody repsonse?

Answer 39

high IgM at beginning --> upregulating response high IgG later --> downregulating response