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immunology > 10. Lymphocyte development and Antigen receptor Gene rearrangement > Flashcards

10. Lymphocyte development and Antigen receptor Gene rearrangement Flashcards

1
Q

what do lymphocytes start as

A

stem cells

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2
Q

where do B cells begin

A

Bone marrow

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3
Q

what happens after stem cells

A

pro lymphocyte

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4
Q

made after pro-lymphocyte

A

pre lymphocyte

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5
Q

what does an pre-lymphocyte become

A

immature lymphocyte

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6
Q

where does an immature lymphocyte become a mature lymphocyte and what is different

A

peripheral lymphoid organ or tissue and become antigen dependent

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7
Q

what are the series of events that occur for B and T cell production

A

commitment, proliferation, rearrangement of Ag receptor genes, selection events, Differentiation

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8
Q

what give rise to B and T cells

A

pluripotent stem cells

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9
Q

what is the role of hematopoietic stem cells (HSC)

A

give rise to common lymphoid progenitor (CLP)

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10
Q

what do CLPs produce

A

B cells, T cells, and NK cells

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11
Q

what type of B cells can a Pro B cell from a CLP become

A

follicular, marginal zone, B1

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12
Q

what type of T cells can a pro t cell become

A

aB T and yDelta T

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13
Q

what TF make a pro B cell from CLP

A

EBF, E2A, Pax5

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14
Q

what are the steps for a Pro T to be made from CLP

A

T cell precursor from CLP then Notch 1 and GATA 3 make a Pro T

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15
Q

what stimulates the proliferation of commited B and T cells

A

cytokines

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16
Q

what is proliferation so important

A

need a large pool of progenitor cells to generate high diversity of mature lymphocytes

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17
Q

why is Ag receptor arrangement important

A

provides survival signals for the cell

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18
Q

what cytokine provides the proliferation of T human cell progenitors and where

A

IL 7 produced from stromal cells in the thymus

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19
Q

what cytokine leads to the proliferation of NK cells

A

IL 15

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20
Q

what cytokines lead to B cell development

A

unknown

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21
Q

what is the ultimate determining factor for B and T cell commitment

A

signals from Ag receptors

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22
Q

what do signals from cell surface receptors activate

A

TF that induce Gene expression and rearrangement of Ag receptor genes

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23
Q

what allows for gene expression and rearrangement in developing B cells

A

Ig Heavy chain locus opens and becomes accessible to proteins

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24
Q

what in Developing aB T cells allows for TCR gene expression and rearrangement

A

TCR gene locus opens

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25
Q

what type of proteins are Notch

A

cell surface molecules

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26
Q

how do Notch proteins work

A

proteolytically cleaved when interact with ligands of neighboring cells

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27
Q

what does the cleavage of Notch proteins lead to

A

intracellular portion migrates to nucleus to modulate expression of target genes

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28
Q

which cells does GATA 3 effect the gene expression of

A

aB T cells

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29
Q

what is the type of recombination that occurs for pre TCR genes

A

V (D) J

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30
Q

what genes are expressed for B cell development

A

Rag1 and 2 proteins, surrogate light chains, Iga and IgB signaling proteins

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31
Q

what do Rag 1 and 2 proteins do

A

regulate BCR rearrangement

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32
Q

what is the surrogate light chain for in B cell development

A

pre-B cell receptor

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33
Q

what are the epigenetic mechanism used for B and T cell development

A

DNA methylation, silence Non-coding RNAs, modify histone tells of nucleosomes

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34
Q

what is methylated to silence genes

A

cytosine residues

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35
Q

is modification of histone tails activate or inactivate genes

A

both

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36
Q

what is the goal of epigentics

A

make genes available or unavailable in chromatin

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37
Q

euchromatin

A

loosely packed chromatin for TC

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38
Q

silenced genes have chromatin in what state

A

heterochromatin

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39
Q

what types of modifications are done to histone tails

A

acetylation, methylation, ubiquitination

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40
Q

how are chromatin remodelled

A

protein remodeling complexes

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41
Q

how does RNA play a role in silencing gene expression

A

non-coding RNAs can silence it

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42
Q

main type of non-coding RNA

A

microRNA (miRNA)

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43
Q

how do miRNA work

A

control on a post transcriptional level by impairing translation or promote degradation of mRNA

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44
Q

size of miRNA

A

22 nts

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45
Q

which genes encode Ig

A

u H chain, k chain, upside down y chain

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46
Q

what are the alleles for heavy and light chains

A

VLCL and VHCH

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47
Q

how many alleles of heavy and light chains are expressed on B cells and what does this mean

A

only one of each by allelic exclusion

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48
Q

what does allelic exclusion do

A

governs the expression of TCR and B cells

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49
Q

what is the ratio of maternal to paternal allotype expression

A

equal for so many B and T cells

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50
Q

what are the germlines in stem cells

A

ig and TCR

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51
Q

how are variable regions of T and B cells determined

A

rearrangement of DNA

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52
Q

what do the V and C stand for in alleles of stem cells

A

variable and Constant

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53
Q

what is DNA chromosomal rearrangement the major mechanism for

A

epitope-specific diversity of BCR and TCR

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54
Q

3 mechanism of DNA rearrangement

A

Somatic recombination, mRNA splicing, junctional diversity

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55
Q

what do the 3 mechanisms of DNA rearrangement involve

A

deletion and reannealing of gene segments

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56
Q

what are the segments on BCR and TCR

A

variable, Diversity and Joining segments

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57
Q

what do VDJ stand for

A

variable, diversity and segments

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58
Q

what parts of BCR have diversity segment

A

Heavy chain

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59
Q

what part of TCR aB has diversity segment

A

Beta

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60
Q

which part of BCR does not have repertoire with junctional diversity

A

lambda

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61
Q

what determines which chromosome: maternal or paternal, is used

A

first for gene rearrangement

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62
Q

4 gene segments of heavy chain

A

V,D,J and Constant

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63
Q

what chromosome houses Heavy chain genes

A

14

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64
Q

how are all B cells different

A

randomly deletes all but one copy of VDJ segments so all are different

65
Q

RAG=

A

random activating genes

66
Q

what do RAG 1 and 2 do

A

encode enzymes for VDJ recombination of BCR and TCR

67
Q

what is RAG 1 and 2 expression restricted to

A

B and T lymphocytes during developmental stages

68
Q

Pre B cells are made up of what chains

A

u heavy and surrogate light chains

69
Q

how are DNA segments present in a mature B cell

A

single copy of each segment

70
Q

1st deletion for B cell diversity

A

D and J chosen with DNA between them deleted

71
Q

2nd step in B cell deletion

A

V is chosen and DNA between it and DJ deleted

72
Q

3rd step in deletion of B cell segments

A

C is chosen then DNA between it and VDJ is deleted

73
Q

what is the chance of having a productive rearrangement

A

10%

74
Q

what is a productive rearrangement

A

B cell segments without a stop codon

75
Q

how are productive rearrangements confirmed

A

test with TC and TL

76
Q

what happens once productive is confirmed

A

recombination of other segments stops

77
Q

how are Ig M or IgD molecules made

A

Tc driven by promoter to produce u or delta heavy chain by alternative splicing

78
Q

where are IgM and IgD first made

A

cell surface of naive B cells

79
Q

what produces secondary isotypes

A

class-switch recombination

80
Q

how do CSRs work

A

exchanges constant region of Heavy chain with dow stream constant region genes

81
Q

what enzyme is required for Ig Class switching

A

Activation-induced cytidine deaminase

82
Q

What does AID do

A

creates DNA breaks at switch (S) regions

83
Q

where are S regions located

A

before Constant regions

84
Q

what happens after AID cuts

A

DNA repair

85
Q

what happens if VH rearrangement is productive

A

B cells proliferate and take care of VL

86
Q

what are they type of light chains in BCR

A

k and lambda

87
Q

which VL do not have D segments

A

k and lambda

88
Q

how does recombination work for VL

A

same as VH with productive rearrangement test

89
Q

each B cells has what type of chains

A

one VH and one VL

90
Q

where is k chain located

A

2nd chromosome

91
Q

where is lambda chain located

A

22nd chromosome

92
Q

how many C regions will a heavy chain have

A

3

93
Q

what are the segments in TCR a and B chains

A

V J and C and D

94
Q

how many of each segment is in a chain of TCR

A

V has 70-80 copies, J has 61 copies

95
Q

how many copies of segments in B chain of TCR are their

A

V has 52, J has 6 the 2 D the 7 J, 2 C

96
Q

steps in TCR gene rearrangement

A

same with same enzyme as BCR

97
Q

how many different TCR are their

A

3 x 10^6

98
Q

how many different BCRs are their

A

10^6

99
Q

what further increases the diversity of TCR and BCR besides VDJ recombination

A

Junctional diversity

100
Q

what is the junctional diversity of TCRs and BCRs

A

10^16 and 10^11

101
Q

where is junctional diversity generated

A

points between joining genes

102
Q

what causes junctional diversity

A

loss of nucleotides by exonucleases and addition of N and P nucleotides

103
Q

how are P nucleotides made

A

asymmetric opening of hairpin loops

104
Q

what do self- complementarity of P nucleotides lead to

A

palindromic appearance

105
Q

what do P nucleotides produce

A

openings of short single stranded extensions that can be incorporated into junctions and removed via exonuclease activity

106
Q

How is RAG and P nucleotides related

A

Rag Cleaves Hairpin loops and adds P nucleotides

107
Q

what adds N nucleotides and where

A

terminal Deoxynucleotidyl Transferase (TdT) adds N to P nucleotides and other strand

108
Q

what type of diversity does VDJ provide

A

combinatorial diversity

109
Q

what is the same in all B and T cells

A

surrogate light chain

110
Q

what do all B and T cells have

A

weak self recognition

111
Q

when are B and T cells chosen for negative selection

A

strong self antigen recognition

112
Q

what is the 1st checkpoint in T and B cell development

A

first polypeptide chain of Ag receptor completed so the H of BCR and the B of TCR

113
Q

2nd checkpoint in B and T cell development

A

production of 2nd polypeptide chain is complete so a in TCR and k or lambda in BCR

114
Q

why are these checkpoints used

A

ensure that Ag receptor gene rearrangement has correctly occurred for mature cells

115
Q

what does selection eliminate

A

harmful self-reactive lymphocytes

116
Q

what makes up a pre ag receptor

A

only one polypeptide chain

117
Q

polypeptide chain in pre BCR

A

u Heavy

118
Q

pre TCR has what chain

A

TCR B chain

119
Q

where can apoptosis of BCR and TCR occur

A

1st and 2nd checkpoint

120
Q

percentage of B and T cells with productive in frame rearragement of 1st polypeptide chain

A

30%

121
Q

what happens to BCR and TCR with out of frame rearrangement

A

Pre not expressed and have apoptosis for no survival signal

122
Q

what signals are provided by pre B and T cells

A

survival, proliferation and further development

123
Q

if 2nd polypep of TCR and BCR has productive rearrangement, what occurs

A

pre to complete but still immature

124
Q

positive selection

A

BCR and TCR with useful ag receptors

125
Q

what do positive selected T cells have

A

CD 8 or CD4 who recognize MHC and not self-Ag

126
Q

where does positive selection occur

A

thymus

127
Q

why is negative selection needed

A

maintain central tolerance of self Ags

128
Q

what does negative selection do

A

eliminate harmful T cells while altering harmful B cells

129
Q

apoptosis of T cells by

A

clonal deletion

130
Q

harmful B cell altered by

A

receptor editing with 2nd Ig rearrangment then if fails then clonal deletion

131
Q

what do B1 cells come from

A

Fetal liver derived stem cells

132
Q

what makes B 2 cells

A

Bone marrow precursors

133
Q

why do B1 cells have limited BCR diversity

A

no TdT in fetal liver so no junctional diversity

134
Q

where are most B1 cells found

A

self renewing in peritoneum and mucosal sites

135
Q

what is secreted by B1 cells

A

IgM Abs

136
Q

what are IgM for

A

react with Microbial polysacharides and lipids, oxidized lipids

137
Q

what bacteria are most effected by IgM

A

Gram +

138
Q

which antibodies are natural

A

IgM

139
Q

what provides most of the IgM levels in early phases of infection

A

B1-B cells

140
Q

what happens once immature B2 cells are made

A

relocated to the spleen

141
Q

what do B2 cells become

A

marginal zone cells or follicular cells

142
Q

where are follicular B cells found

A

recirculating lymphocytes

143
Q

where are MZ cells found

A

spleen and lymph nodes

144
Q

where in spleen do MZ cells go

A

splenic marginal zone, near marginal sinus

145
Q

what do MZ cells respond to

A

Blood borne Ags

146
Q

what is requires replenishment from bone marrow

A

F B cells

147
Q

what do F B cells respond to

A

protein Ag

148
Q

what are F B cells dependent on

A

T cells

149
Q

what do F B cells easily undergo

A

isotype switching and affinity maturation

150
Q

mature F cells become

A

long lived plasma or memory B cells

151
Q

MZ are independent of

A

T cells

152
Q

MZ respond and produce

A

to polysaccharide Ags and generate natural Abs

153
Q

which organs house MZ cells

A

spleen and lymph nodes

154
Q

which microbes to MZ cells react on and what do they produce

A

blood borne microbes and make short lived IgM plasma cells

155
Q

what is mediated by MZ cells

A

T cell independent humoral immune response to circulating pathogens and some T cell dependent

156
Q

Rearrangement of TCR B, y, sigma is initiated

A

simultaneously

157
Q

what happens for a TCR to be of y sigma origin

A

rearranges before B

158
Q

what percent of T cells are y sigma

A

10%

159
Q

why do y sigma TCR have limited diversity

A

very few VDJ segments

immunology (10 decks)

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