#3 Anibody Diversity 01.09

Question 1

name 3 things that contribute to the diverse B cell repertoire

Answer 1

1. somatic recombination
2. class switching
3. affinity maturation aka somatic hypermutation

Question 2

what is the first step in development of a naive B cell?

Answer 2

rearrange Ig genes, i.e., light and heavy chains

Question 3

what Ig is ALWAYS produced first?

Answer 3

pentameric IgM

Question 4

each Ig molecule produced by any one B cell is ___

Answer 4

identical

Question 5

what is the antibody (Ab) repertoire?

Answer 5

the complete collection of Ab/BCR specificities generated by somatic recombination, circulating through the lymphoid tissue

Question 6

where are B cells made?

Answer 6

bone marrow

Question 7

where does negative selection of B cells occur?

Answer 7

bone marrow

Question 8

where does the B cell precursor rearrange its Ig genes?

Answer 8

bone marrow

Question 9

what is one of the indicators that a B cell is mature?

Answer 9

expression of IgD with IgM

Question 10

what activates a B cell?

Answer 10

binding the proper antigen

Question 11

what do activated B cells give rise to?

Answer 11

plasma cells
memory cells
(bone marrow and lymph tissue)

Question 12

when is a B cell specificity determined?

Answer 12

before infection

Question 13

somatic recombination is antigen ____

Answer 13

independent

Question 14

what 2 enzymes mediate somatic recombination?

Answer 14

RAG-1 and RAG-2 (recombination activation genes)

Question 15

what happens if you are lacking RAG-1 and/or RAG-2?

Answer 15

no functional lymphocytes aka B or T cells

Question 16

what region of the Ig is somatic recombination generating?

Answer 16

the variable region of the light and heavy chains

Question 17

what combines to make the light chain variable region?

Answer 17

V+J

Question 18

what are the two types of light chains?

Answer 18

kappa and lambda

Question 19

can a B cell have both kappa and lambda light chains?

Answer 19

no! only one

Question 20

what is the extra gene segment that heavy chains have as compared to light chains?

Answer 20

D

Question 21

gene segmentation difference between kappa and lambda light chains

Answer 21

kappa: all the Js, then a single C
lambda: J and C alternating

Question 22

what is allelic exclusion?

Answer 22

when B cell chain rearrangement occurs, it only happens on one chromosome at a time, otherwise a B cell would express 2 Ab at once

Question 23

what occurs first, heavy or light chain rearrangement?

Answer 23

heavy

Question 24

what region is changed during class switching?

Answer 24

the constant region of the heavy chain

Question 25

what region is changed during somatic recombinaton?

Answer 25

variable region of heavy (VDJ) and light (VJ)

Question 26

what combines to make the heavy chain variable region?

Answer 26

V+D+J

Question 27

3 things that create diversity of BCR molecules in somatic recombination:

Answer 27

1. V+J or V+D+J giving many different variable regions of light and heavy chains, respectively 2. the pairing of light and heavy chains 3. the imprecise joining process of the gene segments (NT that randomly hang on edge)

Question 28

what is the order of events in somatic recombination of light and heavy chains?

Answer 28

somatic recombination (of germline DNA) --> Tx (of the rearranged DNA) --> spicing out of introns (from 1* RNA transcript) --> TL (of RNA) --> polypeptide chain = Ig

Question 29

order of somatic recombination for the variable region of a heavy chain

Answer 29

1. D+J | 2. V+DJ

Question 30

how many Ab/BCRs are coded for by Ig genes?

Answer 30

~10^11

Question 31

order of Ig heavy chain constant region gene segments ***

Answer 31

``` Cμ = IgM Cδ = IgD Cγ3 = IgG3 Cγ1= IgG1 Cα1 = IgA1 Cγ2 = IgG2 Cγ4 = IgG4 Cε = IgE Cα2 = IgA2 ```

Question 32

what is the one Ig gene segment that does not have a preceding switch region?

Answer 32

IgD

Question 33

where does recombination occur during class switching?

Answer 33

at the switch region

Question 34

what stage of development is the B cell in when it is undergoing class switching? where is its location?

Answer 34

B cell is already activated | proliferating in germinal center Rxn

Question 35

what is a terminally class-switched B cell?

Answer 35

when a cell and all of its daughter cells will express new Ig/Ab bc all other heavy chain options have been deleted

Question 36

what is the one Ab type that you cannot class switch to?

Answer 36

IgD

Question 37

which Ab has no significant secretion?

Answer 37

IgD

Question 38

which Ab do you always make first?

Answer 38

IgM

Question 39

when a B cell is mature, it expresses...

Answer 39

IgM | IgD

Question 40

what is somatic hypermutation/affinity maturation?

Answer 40

mutation that occurs at high frequency in the rearranged variable-region DNA of Ig genes in activated B cells

Question 41

what does somatic hypermutation/affinity maturation result in?

Answer 41

production of variant Ab | some have higher affinity for antigen

Question 42

in somatic hypermutation, which B cells are positively selected for?

Answer 42

those that express higher affinity Ab

Question 43

in somatic hypermutation/affinity maturation, B cells that express ____ affinity for Ab are ____ selected for

Answer 43

higher | positively

Question 44

quick-hand version of the constant region of heavy chain

Answer 44

``` M D G3 G1 A1 G2 G4 E A2 ```

Question 45

three mechanisms for generation of Ab diversity

Answer 45

1. cassette system of gene segments via somatic recombination 2. class switching 3. somatic hypermutation/affinty maturation

Question 46

somatic recombination is Ab ____

Answer 46

independent

Question 47

class switching is Ab ____

Answer 47

dependent

Question 48

somatic hypermutation is Ab ____

Answer 48

dependent

Question 49

what changes and what doesn't change in class switching?

Answer 49

changes: the isotype the B cell produces | no change: the antigen specificity

Question 50

what is a critical growth factor that is necessary to mature B cells?

Answer 50

IL-7

Question 51

what produces IL-7?

Answer 51

stromal cells in bone marrow

Question 52

what stage do B cells begin responding to IL-7?

Answer 52

late pro-B cell

Question 53

name the stages of B cell development**

Answer 53

1. stem cell 2. early pro-B cell 3. late pro-B cell 4. large pre-B cell 5. small pre-B cell 6. immature B cell 7. mature B cell

Question 54

B cell development: stem cell

Answer 54

germline for both heavy and light chains

Question 55

B cell development: early pro B

Answer 55

D-J begin heavy chain rearranging of variable region :: no surface Ig

Question 56

B cell development: late pro B

Answer 56

V-DJ fully rearranged heavy chain variable coding region :: no surface Ig

Question 57

B cell development: large pre-B cell

Answer 57

VDJ | translation of heavy chain

Question 58

B cell development: small pre B

Answer 58

V-J | begin light chain rearrangement of variable region

Question 59

B cell development: immature B cell

Answer 59

VJ light chain fully rearranged begin expressing IgM

Question 60

B cell development:

Answer 60

IgD and IgM expressed

Question 61

what can IgD do? what can it not do?

Answer 61

can do: bind antigens as well (same affinity) as IgM | can't: be secreted in significant amounts

Question 62

what is Bruton's thymidine Kinase (BtK)?**

Answer 62

-involved in signal transduction from cell-surface receptors during B cell development

Question 63

what does a lack of Bruton's thymidine Kinase (BtK) mean?**

Answer 63

lack of B cell repertoire

Question 64

what do RAG-1 and RAG-2 (recombination activation genes) do?**

Answer 64

- make double stranded breaks in DNA during somatic recombination - critical for rearrangement of B and T cell rearrangement of heavy+light/beta+alpha

Question 65

a lack of RAG-1 and RAG-2 (recombination activation genes) means what?**

Answer 65

wont' have B or T cells / no lymphocytes

Question 66

what is the role of terminal deoxynucleotidyl transferase (TdT)?**

Answer 66

- catalyzes addition of N nucleotides at the junctions between rearranging gene segments of light and heavy chains - backfills gaps

Question 67

what is activation-induced cytidine deaminase (AID)?**

Answer 67

- catalyzes switch recombination (class switching) | - required for somatic hypermutation/affinity maturation

Question 68

what would a lack of activation-induced cytidine deaminase (AID) mean?**

Answer 68

- all Ig would be IgM | - very little ability to increase affinity of Ab for antigens in germinal center Rxn

Question 69

where is the immature B cell self-selected for?

Answer 69

in the bone marrow

Question 70

if an immature B cell comes into contact with something, what is it most likely?

Answer 70

self/host-cell

Question 71

selection of self-tolerant B cells: contact with a multivalent self molecule

Answer 71

death/apop in bone marrow

Question 72

selection of self-tolerant B cells: soluble self molecule

Answer 72

migrates to periphery | anergic B cell

Question 73

describe an anergic B cell

Answer 73

IgD >> IgM :: cannot be activated or respond to stimuli short life span

Question 74

selection of self-tolerant B cells: low affinity noncrosslinking self molecule

Answer 74

migrates to periphery mature B cell :: IgD and IgM ratio nml becomes part of repertoire unclear of self-reactive or not

Question 75

if a B cell is not positively selected for, what happens?

Answer 75

it fails to enter the lymphoid follicles

Question 76

if a B cell is positively selected for, what happens?

Answer 76

enters lymphoid follicles | stimulation by antigen --> memory B cells, express IgG, IgA, IgE

Question 77

what % of B cells express Ab that have both kappa and lambda light chains?

Answer 77

trick question! | 0%

Question 78

B cell class switching to IgA can be further signaled to class switching to IgG3. T/F

Answer 78

F