Lecture 10: Lymphocyte Development and Antigen Receptor Gene Rearrangement

Question 1

Hematopoietic stem cells give rise to ___ which give rise to

Answer 1

Common lymphoid progenitors CLPs which give rise to B cells, T cells and NK cells

Question 2

What happens when Pre-Ag receptor is successfully rearranged

Answer 2

It provides survival signals that select the cell

Question 3

What drives the proliferation of human T cell progenitors and where is it produced

Answer 3

IL-7 produced in the thymus

Question 4

What other function does IL-7 have besides proliferation of T cells

Answer 4

When produced by stromal cells in bone arrow, it promotes B cell development

Question 5

What drives development of NK cells and where

Answer 5

IL-15 in the thymus

Question 6

First step in developing B cells

Answer 6

The Ig heavy chain locus opens up and becomes accessible to proteins that will mediate Ig gene rearrangement and expression

Question 7

First step in developing a/b T cells

Answer 7

The TCR beta gene locus opens up and becomes accessible for TCR gene rearrangement and expression

Question 8

Which transcription factors commit cells to the T cell lineage

Answer 8

Notch-1 and GATA-3

Question 9

Function of Notch protein

Answer 9

Notch is cleaved and intracellular portion travels to nucleus to modulate expression of target genes
GATA3 also helps induce this expression

Question 10

Which proteins regulate TCR/BCR rearrangement

Answer 10

Rag-1 and Rag-2

Question 11

Which genes undergo V(D)J recombination

Answer 11

Those which encode the components of pre-TCR

Question 12

Which TFs induce expression of genes for B cell development

Answer 12

EBF, E2A and Pax-5

Question 13

DNA methylation on cytosine results in

Answer 13

Gene silencing

Question 14

Allelic exclusion refers to

Answer 14

The restriction that only one of the light chain and heavy chain alleles (maternal or paternal) is expressed in a single B cells

Question 15

Variable regions of the chains in T and B cells are determined by

Answer 15

Rearrangement of the DNA

Question 16

What is the major mechanism of epitope-specific diversity of BCR/TCRs

Answer 16

DNA chromosomal rearrangement

Question 17

The process of rearrangement includes

Answer 17

Deletions of DNA/RNA nucleotides and reannealing gene segments.
This is done by Rag1 and Rag2 recombination enzymes and is called V(D)J recombination

Question 18

RAG-mediated DNA breaks are repaired exclusively by

Answer 18

Non homologous end joining

Question 19

Three mechanisms of rearranging gene segments

Answer 19

Somatic recombination
mRNA splicing
Junctional diversity

Question 20

How does each B cell generate unique combinations of V(D)J segments

Answer 20

In a single B cell all copies but one each of VDJ are randomly deleted

Question 21

Recombination starts with which chain in B and T cells, respectively, and then moves to which chain

Answer 21

Starts with heavy chain in B cells
Starts with Beta chain in T cells
If functional, rearrangement of light chain (B cells) or alpha-chain (T cells) occurs

Question 22

Achieving BCR diversity heavy chain step one

Answer 22

First, D and J are chosen and DNA between them is deleted

Question 23

Achieving BCR diversity heavy chain step two

Answer 23

Second, a V segment is chosen and DNA between V and DJ is deleted

Question 24

Achieving BCR diversity heavy chain step three

Answer 24

Third, a C is chosen and DNA between VDJ and C is deleted

Question 25

What is the chance % of producing a productive rearrangement (w/o stop codons in sequence)

Answer 25

10%

Question 26

H-chain chromosome K-chain chromosome Lambda-chain chromosome

Answer 26

H-14 K-2 L-22

Question 27

THE VDJ rearrangement segment facilitates the synthesis of _________, and is controlled by ______

Answer 27

Facilitates synthesis of a Mu or delta heavy chain, controlled by alternative mRNA splicing This then associates with lightchain forming IgM or IgD molecule

Question 28

Non-IgM/IgD heavy chains are produced by ______, which is a process that

Answer 28

Class-switch recombination (CSR), a process that exchanges the constant region of the heavy chain

Question 29

Class switch recombination (CSR) requires what enzyme that is only expressed at what time

Answer 29

AID- only expressed in activated B cells

Question 30

AID method of operation

Answer 30

AID introduces uracil residues into DNA of S (switch) regions, inducing generation of DNA breaks at these regions followed by repair

Question 31

Junctional diversity

Answer 31

TdT and/or RAG adds or removes nucleotides to the exposed ends of the V, (D) or J genes before they are reunited

Question 32

Junctional diversity is helpful how

Answer 32

It increases the diversity of TCRs and BCRs

Question 33

Junctional diversity is created where

Answer 33

At the points between joining genes

Question 34

Junctional diversity results from

Answer 34

The loss of nucleotides through action of exonucleases and the addition of N and P nucleotides

Question 35

RAG and TdT function in junctional diversity

Answer 35

RAG cleaves hairpin loops and adds P nucleotides (P nucleotides form from asymmetric opening of hairpin) TdT adds N nucleotides

Question 36

Checkpoint #1 of the selection process

Answer 36

After the production of the first polypeptide chain of the two-chain Ag receptor is completed

Question 37

Checkpoint #2 of the selection process

Answer 37

Follows the production of the second polypeptide chain of the Ag receptor

Question 38

Pre-Ag receptor structure

Answer 38

Pre-Ag receptors contain only one polypeptide chain present in mature Ag receptor and a surrogate receptor chain

Question 39

Pre-BCRs contain

Answer 39

Ig(Mu) heavy chain

Question 40

Pre-TCRs contain

Answer 40

TCR Beta chain

Question 41

What is the first Ag receptor gene to be completely rearranged in B cells

Answer 41

Ig heavy chain

Question 42

Developing B cells that successfully rearrange their Ig heavy chain genes then express

Answer 42

The Mu heavy chain protein and assemble the pre-BCR

Question 43

Developing T cells that make productive TCR B chain gene rearrangement synthesize

Answer 43

The TCR B chain protein and assemble the pre-TCR

Question 44

What percent of B/T cells make a productive in-frame rearrangement

Answer 44

30%

Question 45

Assembled pre-BCRs/TCRs provide signals for

Answer 45

Survival, proliferation and further development of early B/T cell lineages

Question 46

Negative/positive selection is part of what checkpoint

Answer 46

Checkpoint 2

Question 47

If cells make productive rearrangement of second chain, they express

Answer 47

Complete Ag receptor while they are still immature. These cells will be positively selected

Question 48

What is important for maintaining the central tolerance to many self Ags

Answer 48

Negative selection

Question 49

When does negative selection occur

Answer 49

Shortly after Ag receptors are first expressed on developing B/T cells

Question 50

Negative selection effect on T cells vs B cells

Answer 50

It will eliminate harmful T cells but ALTER harmful b cells whose Ag receptors bind strongly to self Ags in thymus/bone marrow

Question 51

Clonal deletion

Answer 51

Process of eliminating harmful T cells

Question 52

Receptor editing

Answer 52

Second attempt at Ig gene rearrangement, if this fails, B cells will enter clonal deletion

Question 53

What chain will be altered first in a B cell that binds self Ags. What chain will be altered second?

Answer 53

Kappa Light chain will be rearranged first | Lambda light chain is rearranged second, if needed

Question 54

B cells developing from fetal liver-derived stem cells differentiate into

Answer 54

B-1 lineage

Question 55

B cells developing from bone marrow precursors give rise to

Answer 55

B-2 lineage

Question 56

B-1 cell receptor diversity

Answer 56

Limited BCR diversity because TdT is not expressed in the fetal liver Without TdT- no junctional diversity

Question 57

B-1 cells are found where and secrete what

Answer 57

Found in peritoneum and mucosal sites | Spontaneously secrete IgM that react with polysaccharides/lipids/oxidized lipids

Question 58

B-1 B cell involvement in early phases of infection

Answer 58

Contribute most of the serum IgM during early phases

Question 59

Immature B-2 B cells relocate where after what

Answer 59

After rearrangement of BCR chain genes, they relocate to spleen

Question 60

B-2 cells can differentiate into

Answer 60

Marginal zone MZ B cells or Mature follicular FO B-2 cells

Question 61

FO B-2 cells are

Answer 61

Recirculating lymphocytes

Question 62

MZ B-2 cells are abundant where but also found where

Answer 62

Abundant in spleen (in marginal sinus), also found in lymph nodes

Question 63

MZ B cells respond to

Answer 63

Blood-borne pathogens

Question 64

Responses of MZ B cells are independent or dependent on T cell help

Answer 64

Independent of T cell help (usually) but can mediate SOME T cell dependent immune responses They are self renewing

Question 65

FO B-2 cells may develop into plasma/memory cells depending upon

Answer 65

Mature FO B-2 cells depend upon T cell activation to mature into plasma/memory cells

Question 66

True or False - MZ B cells undergo immunoglobulin isotype switching and affinity maturation

Answer 66

Probably false? FO B-2 cells are the ones that do this because they respond to protein Ags in T cell dependent manner

Question 67

MZ B cell diversity

Answer 67

Similar to B-1 cells, they have limited diversity which respond to polysaccharide Ags and generate natural Abs

Question 68

MZ B cells respond very rapidly to ____ and differentiate into what

Answer 68

Respond rapidly to blood borne microbes and differentiate into short-lived IgM secreting plasma cells

Question 69

What causes the limited diversity of expressed gamma/delta TCRs

Answer 69

Only a few of the available V, D and J segments are used in mature yd T cells

Question 70

What determines T cell being yd or ab

Answer 70

If it first succeeds in rearranging its TCR y or delta loci before it makes a productive TCR beta rearrangement, it is selected to the yd T lineage -happens about 10% of time