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Immunology > B cell activation & organization of Immunoglobulin genes > Flashcards

B cell activation & organization of Immunoglobulin genes Flashcards

1
Q

Overview of B cell development

List the following from most immature to most mature

( Pro - B cell, Mature B cell, Activated B cell, Lymphoid cell, Immature B cell, Pre - B cell, Hematopoietic stem cell )

A

Hematopoietic stem cell > Lymphoid cell > Pro - B cell > Pre - B cell > Immature B cell > Mature B cell > Activated B cell

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2
Q

Organization and Expression of Immunoglobulin genes

What does V, D, J, C stands for?

A

V: Variable
D: Diversity
J: Joining
C: Constant

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3
Q

Organization and Expression of Immunoglobulin genes

What is the structural difference between light - chain & heavy - chain?

A

Light chain : V - J arrangement

Heavy chain : V - D - J arrangement

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4
Q

Organization and Expression of Immunoglobulin genes

What are the two light chain gene?

A

Kappa & Lambda

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5
Q

Organization and Expression of Immunoglobulin genes

What is the order in rearranged Kappa - chain DNA?

( Intron x2 , Joined VJ gene segment, constant region, Leader exon )

A

Order :
Leader > Intron > Joined VJ gene segment > Intron > Constant region

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6
Q

Organization and Expression of Immunoglobulin genes

Which sequence in light chain is cleaved in RER?

A

Leader sequance

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7
Q

Organization and Expression of Immunoglobulin genes

Which of the following determines the class of antibodies?

(V, D, J, C)

A

C : Constant

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8
Q

Organization and Expression of Immunoglobulin genes

What are the difference in rearranged Kappa - chain DNA & rearranged Heavy - chain DNA?

A

Kappa :
-> Joined VJ gene segment
-> A constant region

Heavy :
-> Joined VDJ gene segment
-> A series of C gene segments
( For antibody class )

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9
Q

Organization and Expression of Immunoglobulin genes

What is the two class of antibodies that is expressed initially in primary RNA transcription?

A

C(mu) : IgM
C(delta) : IgD

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10
Q

Organization and Expression of Immunoglobulin genes

What is the process that determines whether IgM or IgD is produced?

A

RNA splicing

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11
Q

Organization and Expression of Immunoglobulin genes

Does a mature B cell that expresses both IgM & IgD have the same identical antigenic specificity, and why?

A

Yes

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12
Q

What are the 2 mechanisms of variable - region DNA rearrangements?

A

RSS ( Recombination signal sequences )
-> direct recombination

VDJ recombinases
-> joining gene segment

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13
Q

Organization and Expression of Immunoglobulin genes

What is the 2 types of RSSs? ( Recombination signal sequences )

A

One turn RSS
Two turn RSS

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14
Q

Organization and Expression of Immunoglobulin genes

What are the 2 -amers in RSS?
And whats the properties of it?

A

Heptamer
-> Palindromic

Nonamer
-> AT - rich

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15
Q

Organization and Expression of Immunoglobulin genes

What is the “ One - turn / two - turn joining rule “ about ?

A

One - turn RSS can only join with two - turn RSS

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16
Q

Organization and Expression of Immunoglobulin genes

What is the recombinase enzyme that can recognize RSSs?

A

RAG - 1 / 2
( Recombination - activating gene )

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17
Q

Organization and Expression of Immunoglobulin genes

What is the enzyme that cleave the hairpin structure and trim a few nucleotides from the coding sequence?

A

Endonuclease

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18
Q

Organization and Expression of Immunoglobulin genes

What is the enzyme that adds nucleotides to the cut ends of coding sequence of heavy chain?

A

TdT
( Terminal deoxynucleotidyl transferase )

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19
Q

Organization and Expression of Immunoglobulin genes

What is the enzyme that repair and ligate the coding sequences?

A

DSBR enzymes
( Double - strand break repair )

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20
Q

Does the RAG enzymes cleave both strand of the DNA at the junctures of the RSS and the coding sequence?

A

Nope, they cleave one strand of DNA

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21
Q

Organization and Expression of Immunoglobulin genes

What is P - addition and which 2 enzymes are involved?

A

Cleavage of hairpin by endonuclease
-> Sites for addition of P - nucleotides
- -> DSBR enzymes add complementary nucleotides

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22
Q

Organization and Expression of Immunoglobulin genes

What is N - addition and which 3 enzymes are involved?

A

Cleavage of hairpin by endonuclease
-> Sites for addition of P - nucleotides
- -> DSBR enzymes add complementary nucleotides
- - -> TdT adds N - nucleotides

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23
Q

Organization and Expression of Immunoglobulin genes

Does N - addition happens in both light chain and heavy chain?

A

Nope
It only happens in heavy chain

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24
Q

Organization and Expression of Immunoglobulin genes

What is junctional flexibility?

A

The selection of which nucleotide in two coding sequences (e.g. V & J / D & J) to be joined together can be completely random.

E.g. V ( ATG ) & J ( CGC )
-> ATGCGC
-> ATGGC
-> ACGC
-> ATCGC
etc

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25
Q

Organization and Expression of Immunoglobulin genes

What is the disadvantage of junctional flexibility?

A

It can produce stop codons which interrupt translation

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26
Q

Organization and Expression of Immunoglobulin genes

What are the 5 things that creates antibody diversity?

A

V(D)J rearrangement
P - region nucleotide addition
N - region nucleotide addition
Junctional flexibility
Somatic hypermutation

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27
Q

Organization and Expression of Immunoglobulin genes

Which of the following occurs in bone marrow / germinal center?

V(D)J rearrangement
P - region nucleotide addition
N - region nucleotide addition
Junctional flexibility
Somatic hypermutation

A

Bone marrow :
V(D)J rearrangement
P - region nucleotide addition
N - region nucleotide addition
Junctional flexibility

Germinal center :
Somatic hypermutation

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28
Q

Organization and Expression of Immunoglobulin genes

What is the mutation rate in somatic hypermutation? 10 ^ (??) / bp / mutation

A

10 ^ (-3) / bp / mutation

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29
Q

Organization and Expression of Immunoglobulin genes

Somatic hypermutation guarantees at least one mutation per every (??) division

A

Two

30
Q

Organization and Expression of Immunoglobulin genes

What is allelic exclusion?

A

Allelic exclusion ensures single antigenic specificity

31
Q

Organization and Expression of Immunoglobulin genes

In allelic exclusion, what is first produced in progenitor B cell?

A

D and J component of VDJ heavy chain

32
Q

Organization and Expression of Immunoglobulin genes

In allelic exclusion, which is the first allele checked?

A

Mu heavy chain (Mu allele #1)

33
Q

Organization and Expression of Immunoglobulin genes

In allelic exclusion, what does Mu heavy chain (Mu allele #1) inhibits & induces?

A

Inhibits rearrangement of the Mu allele #2

Induces Kappa rearrangement

34
Q

Organization and Expression of Immunoglobulin genes

In allelic exclusion, what is the second allele checked after Mu heavy chain (Mu allele #1) is productive?

A

Kappa light chain (Kappa allele #1)

35
Q

Organization and Expression of Immunoglobulin genes

In allelic exclusion, what happens when both Mu heavy chain (Mu allele #1) & Kappa light chain (Kappa allele #1) are productive alleles?

A

Antibodies are successfully produced

36
Q

Organization and Expression of Immunoglobulin genes

In allelic exclusion, what does Mu heavy chain (Mu allele #1) & Kappa light chain (Kappa allele #1) inhibits & induces?

A

Inhibits
-> rearrangement of the Kappa allele #1
-> Lambda rearrangement

Induces nothing

37
Q

Organization and Expression of Immunoglobulin genes

In allelic exclusion, what happens if Kappa light chain (Kappa allele #1) is nonproductive?

A

Kappa light chain (Kappa allele #2) is checked

38
Q

Organization and Expression of Immunoglobulin genes

In allelic exclusion, what if both Kappa light chain (Kappa allele #1 & #2) are nonproductive?

A

Lambda light chain ( Lambda allele #1) is checked

39
Q

Organization and Expression of Immunoglobulin genes

In allelic exclusion, what does Mu heavy chain (Mu allele #1) & Lambda light chain (Lambda allele #1) inhibits & induces?

A

Inhibits rearrangement of Lambda allele #2

40
Q

Organization and Expression of Immunoglobulin genes

In allelic exclusion, what happens if both Mu allele are nonproductive?

A

Apoptosis

41
Q

Organization and Expression of Immunoglobulin genes

In allelic exclusion, what happens if both Kappa allele & Lambda allele are nonproductive?

A

Apoptosis

42
Q

Organization and Expression of Immunoglobulin genes

Which two class of membrane bound antibodies are simultaneously expressed in mature naïve B cell?

A

mIgM & mIgD

43
Q

Organization and Expression of Immunoglobulin genes

What are the difference between sIgM & mIgM?

A

sIgM
-> Contains hydrophilic portion that are encoded by S exon of C(mu)

mIgM
-> Contains both hydrophilic & hydrophobic portion that are encoded by M1 & M2 exons of C(mu)
- -> Hydrophilic : Outside + Cytoplasm
- -> Hydrophobic : Membrane

44
Q

Organization and Expression of Immunoglobulin genes

What processing action in RNA transcription causes the difference between sIgM & mIgM?

A

RNA splicing

45
Q

Organization and Expression of Immunoglobulin genes

Which of the two organelles is essential for sIg production?

A

RER & Golgi

46
Q

Organization and Expression of Immunoglobulin genes

What are the 4 things that happen in RER for sIg production?

A

Translation of heavy chain & light chain
Cleavage of Leader sequence
Assembly of heavy chain & light chain to form monomer
Assembly of monomers to form homodimer

47
Q

Organization and Expression of Immunoglobulin genes

What are the 2 things that happen in Golgi for sIg production?

A

Post translational modification of homodimer
-> Addition of oligosaccharide
Packaged by secretory vesicles

48
Q

Organization and Expression of Immunoglobulin genes

What is the difference in Secretion between sIg & mIg

A

Same thing happens in RER & Golgi

However
-> Hydrophobic part of mIg becomes embedded on the membrane of secretory vesicle
-> Fusion of secretory vesicle with cell membrane causes mIg to stay on the membrane instead of being released

49
Q

Organization and Expression of Immunoglobulin genes

What are the 3 types of regulatory elements in Ig genes?

A

Promoters

Enhancers

Silencers

50
Q

Organization and Expression of Immunoglobulin genes

Where can promoters be found and what does it do?

A

200 bp upstream from transcription initiation site

Promotes initiation of RNA transcription in a specific direction

51
Q

Organization and Expression of Immunoglobulin genes

Where can enhancers be found and what does it do?

A

upstream / downstream of genes ( in this case VDJ )

It can stimulate promoter to initiate transcription regardless its position / direction

52
Q

Organization and Expression of Immunoglobulin genes

Where can silencer be found and what does it do?

A

upstream or downstream of genes
( in this case VDJ )

It can inhibit / repress gene transcription regardless its position / direction

53
Q

Organization and Expression of Immunoglobulin genes

Does each V ( heavy chain ) & V ( light chain ) segment has a promoter & leader sequence?

A

Yes

54
Q

Organization and Expression of Immunoglobulin genes

Which of the following DNA does not contain silencers?

Heavy chain DNA
Kappa chain DNA
Lambda chain DNA

A

Lambda chain DNA

55
Q

Organization and Expression of Immunoglobulin genes

Explain the mechanism in class switching ( from IgM -> IgA ), Including the following words

Switch region
Constant exon region
Switch recombinase

A

In C gene after VDJ genes
There are switch region right before every different constant exon region
(e.g. S(IgM) C(IgM) S (IgD) C(IgD) )

When B cell desires to switch IgM class to IgA
Switch recombinase aids in forming a loop from S(IgM) -> C(IgE) )
( According to order IgM/D/G/E/A )

Removal of the loop brings S(IgA) in proximity to VDJ genes, allowing transcription of VDJ C(IgA)

56
Q

Organization and Expression of Immunoglobulin genes

What is the switch factor (cytokine)?

A

IL - 4

57
Q

B - cell Maturation, Activation & Differentiation

How long can plasma cell survive?

A

1 - 2 weeks

58
Q

B - cell Maturation, Activation & Differentiation

What is the function of IL - 7?

A

It down regulates the adhesion molecules

59
Q

B - cell Maturation, Activation & Differentiation

What triggers the expression of IL - 7 receptor on Pre - B cells?

A

Binding of c-Kit -> SCF

*c-Kit -> Bone marrow stromal cell
SCF -> Pro - B cell

60
Q

B - cell Maturation, Activation & Differentiation
What is the protein that help transduce activating signals of mIg on B cell ?

A

Ig - alpha / Ig - beta heterodimers

61
Q

B - cell Maturation, Activation & Differentiation

What are the two signals that drive B cells into & through the cell cycle?

A

Ag - mIg

CD40L

62
Q

B - cell Maturation, Activation & Differentiation
What does Ag - mIg induce?

A

Expression of MHC - 2 & B7 on B cell

63
Q

B - cell Maturation, Activation & Differentiation
What is the purpose of expressing MHC - 2 on B cell?

A

Recognization of MHC - 2 by Th cell activates Th cell

64
Q

B - cell Maturation, Activation & Differentiation
What is the purpose of expressing B7 on B cell?

A

Allow B7 - CD28 interactions which co - stimulate Th cell with MHC - 2 recognition

65
Q

B - cell Maturation, Activation & Differentiation
What happens when Th cell is activated by the co - simulation?

A

Th cell begins to express CD40L
-> Interaction between CD40 & CD40L (2)

66
Q

B - cell Maturation, Activation & Differentiation

What happens after both signals is present & active?

A

B cells express cytokines receptor
Th cell release cytokines
-> IL - 2
-> IL - 4
-> IL - 5
Signals supports progression of B cell
-> DNA synthesis
-> Differentiation

67
Q

B - cell Maturation, Activation & Differentiation
Which of the following cytokine induce class switch to
IgG2a / IgG3?

IL - 2
IL - 4
IL - 5
IFN - gamma
TGF - beta

A

IFN - gamma

68
Q

B - cell Maturation, Activation & Differentiation
Which of the following cytokine induce class switch to
IgA / IgG2b?

IL - 2
IL - 4
IL - 5
IFN - gamma
TGF - beta

A

TGF - beta

69
Q

B - cell Maturation, Activation & Differentiation
Which of the following cytokine induce class switch to
IgE / IgG1?

IL - 2
IL - 4
IL - 5
IFN - gamma
TGF - beta

A

IL - 4

70
Q

B - cell Maturation, Activation & Differentiation
Which of the following cytokine induce class switch to
IgM?

IL - 2
IL - 4
IL - 5
IFN - gamma
TGF - beta

A

IL - 2
IL - 4
IL - 5

71
Q

Match the following

IFN - gamma
TGF - beta Th1
IL - 4
IL - 2 Th2
IL - 5

A

Th1
-> IFN - gamma
-> TGF - beta

Th2
IL - 2
IL - 4
IL - 5

Immunology (8 decks)

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