10. Lymphocyte development and Antigen receptor Gene rearrangement Flashcards
1
Q
what do lymphocytes start as
A
stem cells
2
Q
where do B cells begin
A
Bone marrow
3
Q
what happens after stem cells
A
pro lymphocyte
4
Q
made after pro-lymphocyte
A
pre lymphocyte
5
Q
what does an pre-lymphocyte become
A
immature lymphocyte
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
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
8
Q
what give rise to B and T cells
A
pluripotent stem cells
9
Q
what is the role of hematopoietic stem cells (HSC)
A
give rise to common lymphoid progenitor (CLP)
10
Q
what do CLPs produce
A
B cells, T cells, and NK cells
11
Q
what type of B cells can a Pro B cell from a CLP become
A
follicular, marginal zone, B1
12
Q
what type of T cells can a pro t cell become
A
aB T and yDelta T
13
Q
what TF make a pro B cell from CLP
A
EBF, E2A, Pax5
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
15
Q
what stimulates the proliferation of commited B and T cells
A
cytokines
16
Q
what is proliferation so important
A
need a large pool of progenitor cells to generate high diversity of mature lymphocytes
17
Q
why is Ag receptor arrangement important
A
provides survival signals for the cell
18
Q
what cytokine provides the proliferation of T human cell progenitors and where
A
IL 7 produced from stromal cells in the thymus
19
Q
what cytokine leads to the proliferation of NK cells
A
IL 15
20
Q
what cytokines lead to B cell development
A
unknown
21
Q
what is the ultimate determining factor for B and T cell commitment
A
signals from Ag receptors
22
Q
what do signals from cell surface receptors activate
A
TF that induce Gene expression and rearrangement of Ag receptor genes
23
Q
what allows for gene expression and rearrangement in developing B cells
A
Ig Heavy chain locus opens and becomes accessible to proteins
24
Q
what in Developing aB T cells allows for TCR gene expression and rearrangement
A
TCR gene locus opens
25
what type of proteins are Notch
cell surface molecules
26
how do Notch proteins work
proteolytically cleaved when interact with ligands of neighboring cells
27
what does the cleavage of Notch proteins lead to
intracellular portion migrates to nucleus to modulate expression of target genes
28
which cells does GATA 3 effect the gene expression of
aB T cells
29
what is the type of recombination that occurs for pre TCR genes
V (D) J
30
what genes are expressed for B cell development
Rag1 and 2 proteins, surrogate light chains, Iga and IgB signaling proteins
31
what do Rag 1 and 2 proteins do
regulate BCR rearrangement
32
what is the surrogate light chain for in B cell development
pre-B cell receptor
33
what are the epigenetic mechanism used for B and T cell development
DNA methylation, silence Non-coding RNAs, modify histone tells of nucleosomes
34
what is methylated to silence genes
cytosine residues
35
is modification of histone tails activate or inactivate genes
both
36
what is the goal of epigentics
make genes available or unavailable in chromatin
37
euchromatin
loosely packed chromatin for TC
38
silenced genes have chromatin in what state
heterochromatin
39
what types of modifications are done to histone tails
acetylation, methylation, ubiquitination
40
how are chromatin remodelled
protein remodeling complexes
41
how does RNA play a role in silencing gene expression
non-coding RNAs can silence it
42
main type of non-coding RNA
microRNA (miRNA)
43
how do miRNA work
control on a post transcriptional level by impairing translation or promote degradation of mRNA
44
size of miRNA
22 nts
45
which genes encode Ig
u H chain, k chain, upside down y chain
46
what are the alleles for heavy and light chains
VLCL and VHCH
47
how many alleles of heavy and light chains are expressed on B cells and what does this mean
only one of each by allelic exclusion
48
what does allelic exclusion do
governs the expression of TCR and B cells
49
what is the ratio of maternal to paternal allotype expression
equal for so many B and T cells
50
what are the germlines in stem cells
ig and TCR
51
how are variable regions of T and B cells determined
rearrangement of DNA
52
what do the V and C stand for in alleles of stem cells
variable and Constant
53
what is DNA chromosomal rearrangement the major mechanism for
epitope-specific diversity of BCR and TCR
54
3 mechanism of DNA rearrangement
Somatic recombination, mRNA splicing, junctional diversity
55
what do the 3 mechanisms of DNA rearrangement involve
deletion and reannealing of gene segments
56
what are the segments on BCR and TCR
variable, Diversity and Joining segments
57
what do VDJ stand for
variable, diversity and segments
58
what parts of BCR have diversity segment
Heavy chain
59
what part of TCR aB has diversity segment
Beta
60
which part of BCR does not have repertoire with junctional diversity
lambda
61
what determines which chromosome: maternal or paternal, is used
first for gene rearrangement
62
4 gene segments of heavy chain
V,D,J and Constant
63
what chromosome houses Heavy chain genes
14
64
how are all B cells different
randomly deletes all but one copy of VDJ segments so all are different
65
RAG=
random activating genes
66
what do RAG 1 and 2 do
encode enzymes for VDJ recombination of BCR and TCR
67
what is RAG 1 and 2 expression restricted to
B and T lymphocytes during developmental stages
68
Pre B cells are made up of what chains
u heavy and surrogate light chains
69
how are DNA segments present in a mature B cell
single copy of each segment
70
1st deletion for B cell diversity
D and J chosen with DNA between them deleted
71
2nd step in B cell deletion
V is chosen and DNA between it and DJ deleted
72
3rd step in deletion of B cell segments
C is chosen then DNA between it and VDJ is deleted
73
what is the chance of having a productive rearrangement
10%
74
what is a productive rearrangement
B cell segments without a stop codon
75
how are productive rearrangements confirmed
test with TC and TL
76
what happens once productive is confirmed
recombination of other segments stops
77
how are Ig M or IgD molecules made
Tc driven by promoter to produce u or delta heavy chain by alternative splicing
78
where are IgM and IgD first made
cell surface of naive B cells
79
what produces secondary isotypes
class-switch recombination
80
how do CSRs work
exchanges constant region of Heavy chain with dow stream constant region genes
81
what enzyme is required for Ig Class switching
Activation-induced cytidine deaminase
82
What does AID do
creates DNA breaks at switch (S) regions
83
where are S regions located
before Constant regions
84
what happens after AID cuts
DNA repair
85
what happens if VH rearrangement is productive
B cells proliferate and take care of VL
86
what are they type of light chains in BCR
k and lambda
87
which VL do not have D segments
k and lambda
88
how does recombination work for VL
same as VH with productive rearrangement test
89
each B cells has what type of chains
one VH and one VL
90
where is k chain located
2nd chromosome
91
where is lambda chain located
22nd chromosome
92
how many C regions will a heavy chain have
3
93
what are the segments in TCR a and B chains
V J and C and D
94
how many of each segment is in a chain of TCR
V has 70-80 copies, J has 61 copies
95
how many copies of segments in B chain of TCR are their
V has 52, J has 6 the 2 D the 7 J, 2 C
96
steps in TCR gene rearrangement
same with same enzyme as BCR
97
how many different TCR are their
3 x 10^6
98
how many different BCRs are their
10^6
99
what further increases the diversity of TCR and BCR besides VDJ recombination
Junctional diversity
100
what is the junctional diversity of TCRs and BCRs
10^16 and 10^11
101
where is junctional diversity generated
points between joining genes
102
what causes junctional diversity
loss of nucleotides by exonucleases and addition of N and P nucleotides
103
how are P nucleotides made
asymmetric opening of hairpin loops
104
what do self- complementarity of P nucleotides lead to
palindromic appearance
105
what do P nucleotides produce
openings of short single stranded extensions that can be incorporated into junctions and removed via exonuclease activity
106
How is RAG and P nucleotides related
Rag Cleaves Hairpin loops and adds P nucleotides
107
what adds N nucleotides and where
terminal Deoxynucleotidyl Transferase (TdT) adds N to P nucleotides and other strand
108
what type of diversity does VDJ provide
combinatorial diversity
109
what is the same in all B and T cells
surrogate light chain
110
what do all B and T cells have
weak self recognition
111
when are B and T cells chosen for negative selection
strong self antigen recognition
112
what is the 1st checkpoint in T and B cell development
first polypeptide chain of Ag receptor completed so the H of BCR and the B of TCR
113
2nd checkpoint in B and T cell development
production of 2nd polypeptide chain is complete so a in TCR and k or lambda in BCR
114
why are these checkpoints used
ensure that Ag receptor gene rearrangement has correctly occurred for mature cells
115
what does selection eliminate
harmful self-reactive lymphocytes
116
what makes up a pre ag receptor
only one polypeptide chain
117
polypeptide chain in pre BCR
u Heavy
118
pre TCR has what chain
TCR B chain
119
where can apoptosis of BCR and TCR occur
1st and 2nd checkpoint
120
percentage of B and T cells with productive in frame rearragement of 1st polypeptide chain
30%
121
what happens to BCR and TCR with out of frame rearrangement
Pre not expressed and have apoptosis for no survival signal
122
what signals are provided by pre B and T cells
survival, proliferation and further development
123
if 2nd polypep of TCR and BCR has productive rearrangement, what occurs
pre to complete but still immature
124
positive selection
BCR and TCR with useful ag receptors
125
what do positive selected T cells have
CD 8 or CD4 who recognize MHC and not self-Ag
126
where does positive selection occur
thymus
127
why is negative selection needed
maintain central tolerance of self Ags
128
what does negative selection do
eliminate harmful T cells while altering harmful B cells
129
apoptosis of T cells by
clonal deletion
130
harmful B cell altered by
receptor editing with 2nd Ig rearrangment then if fails then clonal deletion
131
what do B1 cells come from
Fetal liver derived stem cells
132
what makes B 2 cells
Bone marrow precursors
133
why do B1 cells have limited BCR diversity
no TdT in fetal liver so no junctional diversity
134
where are most B1 cells found
self renewing in peritoneum and mucosal sites
135
what is secreted by B1 cells
IgM Abs
136
what are IgM for
react with Microbial polysacharides and lipids, oxidized lipids
137
what bacteria are most effected by IgM
Gram +
138
which antibodies are natural
IgM
139
what provides most of the IgM levels in early phases of infection
B1-B cells
140
what happens once immature B2 cells are made
relocated to the spleen
141
what do B2 cells become
marginal zone cells or follicular cells
142
where are follicular B cells found
recirculating lymphocytes
143
where are MZ cells found
spleen and lymph nodes
144
where in spleen do MZ cells go
splenic marginal zone, near marginal sinus
145
what do MZ cells respond to
Blood borne Ags
146
what is requires replenishment from bone marrow
F B cells
147
what do F B cells respond to
protein Ag
148
what are F B cells dependent on
T cells
149
what do F B cells easily undergo
isotype switching and affinity maturation
150
mature F cells become
long lived plasma or memory B cells
151
MZ are independent of
T cells
152
MZ respond and produce
to polysaccharide Ags and generate natural Abs
153
which organs house MZ cells
spleen and lymph nodes
154
which microbes to MZ cells react on and what do they produce
blood borne microbes and make short lived IgM plasma cells
155
what is mediated by MZ cells
T cell independent humoral immune response to circulating pathogens and some T cell dependent
156
Rearrangement of TCR B, y, sigma is initiated
simultaneously
157
what happens for a TCR to be of y sigma origin
rearranges before B
158
what percent of T cells are y sigma
10%
159
why do y sigma TCR have limited diversity
very few VDJ segments
