Block 1 Lecture 7 -- B Cells and Antibodies

Question 1

What Abs bind exist as dimers?

Answer 1

IgA

Question 2

What Abs exist as pentamers?

Answer 2

IgM

Question 3

What Abs exist as monomers?

Answer 3

IgD
IgG
monomeric IgA
IgE
IgM

Question 4

What makes a B-cell response thymus dependent?

Answer 4

if Ag is protein

Question 5

What are the effects of a helper-T cell response on a B cell?

Answer 5

1) isotype switching
2) affinity maturation
3) memory B cell response

Question 6

What makes a B-cell response thymus-independent?

Answer 6

polymeric Ag (polysaccharides, glycolipids, nucleic acids)

Question 7

What Abs are produced in response to PEG in 10-25% of patients?

Answer 7

IgM (T-independent)

Question 8

What are the effects of a thymus-independent B cell response?

Answer 8

little isotype switching (maybe IgG)
no affinity maturation
no memory response

Question 9

Describe the immunological synapse proteins between a T-B cell interaction.

Answer 9

B cell: pMHCII to TCR

• • CD40 to CD40L
• • CD80/86 to CD28

Question 10

What are the effects of the T-B interaction?

Answer 10

1) T’s produce Tfh cells

2) IL2,4,5 = proliferation of B and short-lived plasma cells

Question 11

Where does affinity maturation, memory response, and isotype switching take place?

Answer 11

in the germinal center of the lymph node (B cell follicle)

Question 12

What cytokine from Th helps produce IgG?

Answer 12

IFN-y (from Th1)

Question 13

What cytokine from Th helps produce IgE?

Answer 13

IL-4 (from Th2)

Question 14

What cytokine helps produce IgA?

Answer 14

mucosal tissue and TGF-beta

Question 15

What is the half-life of IgG?

Answer 15

23 days

Question 16

What Ab has the shortest half-life?

Answer 16

IgE (2 days)

Question 17

Function of IgA?

Answer 17

mucosal immunity

Question 18

Function of IgD?

Answer 18

naive B cell Ag receptor

Question 19

Function of IgE?

Answer 19

helminth immunity, allergy

Question 20

Function of IgG?

Answer 20

opsonization
complement
ADCC
neonatal immunity

Question 21

Function of IgM

Answer 21

naive B cell Ag receptor, complement activation

Question 22

What are examples of overactive B cell disorders?

Answer 22

leukemia, lymphoma, autoimmunity

Question 23

How are overactive B cell disorders treated?

Answer 23

1) Rituximab
2) Immunosuppressants
3) Cell therapy

Question 24

How does rituximab work?

Answer 24

targets CD20 on B cells to stimulate ADCC

Question 25

What is ADCC?

Answer 25

Ab-dependent cell-mediated toxicity (performed by macrophage, monocyte, or NK)

Question 26

What are CAR-T cells?

Answer 26

treatment for ALL, etc. | modified T cells include Ab that kills all B-cells

Question 27

What are examples of underactive B cell disorders?

Answer 27

XLA (X-linked agammaglobulinemia) XHM (X-linked immunodeficiency with hyper IgM) CVID (common variable immunodeficiency)

Question 28

What are therapies for underactive B cells?

Answer 28

IV Ig

Question 29

What is IV Ig?

Answer 29

pooled Abs from healthy donors | readminister q3-4 weeks (igG has 23 day t1/2)

Question 30

How are B cells activated (pathways)?

Answer 30

1) Ag | 2) Complement

Question 31

How is a B cell activated by Ag?

Answer 31

``` BCR dimerization -- Src-TK phosphorylate stuff -- PLC = Ca + DAG, PKC -- Ras pathways generation of TFs ```

Question 32

How is a B cell activated by complement?

Answer 32

Microbe-C3d - - recognized by IgM and CR2 receptors - - kinase pathways

Question 33

Describe B cell development.

Answer 33

Stem -- Pro -- Pre -- Immature -- Mature

Question 34

Characteristics of pro-B cells

Answer 34

proliferation, beginning of mutations

Question 35

Characteristics of pre-B cells

Answer 35

1-chain Ag receptor

Question 36

Characteristics of immature B cells

Answer 36

2-chain Ag (undergoes positive or negative selection)

Question 37

What is a Complimentarity Determining Region

Answer 37

area of hypermutation in DNA of the Ag-binding regions of an Ab

Question 38

How many disulfide bonds in an Ab?

Answer 38

4

Question 39

What changes occur in the antigen-binding region of an antibody?

Answer 39

1) somatic hypermutation | 2) VDJ recombination

Question 40

What changes occur in the Fc portion of an antibody?

Answer 40

isotype switching (heavy chain selection)

Question 41

What is the fx of FcRn

Answer 41

neonatal immunity and longer t1/2

Question 42

What is the mechanism of FcRn?

Answer 42

recycles IgG after endocytosis