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Immune week 6 > VDJ B cell recombination > Flashcards

VDJ B cell recombination Flashcards

1
Q

as B cells proliferate following ANTIGEN CONTACT at secondary LYMPHOID ORGANS, mutations occur PREFERENTALLY in the VDJheavy and VJlight genes, this process if called….

A

somatic hypermutation

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2
Q

B cells at secondary lymphoid organs who are trying to figure what’s the antigen binding site they should have, mutates its antigen binding sites, if these altered ab failed to bind antigen……

A

B cell dies

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3
Q

B cells at secondary lymphoid organs, if they mutate their antigen binding sites that bind antigen better than the original, these B cells….

A

receive stronger signals to proliferate and mature into PLASMA CELLS

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4
Q

As immune reponse progresses, the average affinity of the responding B cells and antibody produced in 2NDARY LYMPHOID ORGANS…….

A

INCREASES this is called AFFINITY MATURATION

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5
Q

Isotype switching increases the………of ab molecules

A

FUNCTIONAL DIVERSITY

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6
Q

Isotype switching deals with the ……of the ab, where as somatic hypermutation invovlves…….

A

ISOTYPE FUNCTIONAL DIVERSITY

SOMATIC HYPERMUTATION mutating its antigen binding sites of Ig to increase the ab affinity to the antigen its presented to

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7
Q

When does isotype switching occur……

A

occurs following ANTIGEN stimulation and TH2 cytokine production

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8
Q

List CH genes in linear order

A

C mu, C delta, C gama3, Cgama1, PSEUDOGENE C epsilon, C alpha 1, C gama 2, Cgama 4, Cepsilon, and Calpha 2

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9
Q

Each C gene segment except….. is preceded by an intron containg a ……sequence

A

C delta

SWITCH REGION

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10
Q

Switch sequences differ from recombination signal sequences found flanking V regions seg

A

True

switch sequences introns, don’t code for nonsense

in vdj you can get nonsense nonfunctional parts

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11
Q

Rearranged VDJHeavy is always expressed……with membrane…..

A

FIRST…Cmu or IgM

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12
Q

Mature B celll has…

A

BOTH MEMBRANE C(mu) and C(delta)

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13
Q

As B cell begins to respond to antigen it secretes……

A

SECRETED C mu IgM

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14
Q

What causes B cells to switch isotopes…..

A

receiving CYTOKINES

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15
Q

The DNA between two switch regions that are recobminating are…..

A

lopped out and removed from genome

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16
Q

All…..are productive since DNA spllicing occurs w/in ……so non nonsense codons are NOT introduced into the transcribed DNA

A

PRODUCTIVE

SPLICING OCCURS in INTRONS

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17
Q

Further switches to down stream isotypes IgA and IgE may occur if the B cell receives the required…..

A

cytokine signal

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18
Q

Genes for ig are UNLIKE other human genes in that

a) each polypeptide chain is encoded by several exons.
b) Ig genes are composed of introns and exons
c) somatic recombination occurs before mRNA is transcribed
d) there is less Ig genetic material in mature B cells than in other somatic cells

A

c) somatic recombination occurs before mRNA is transcribed
d) there is less Ig genetic material in mature B cells than in other somatic cells

Somatic recombination results in loss of DNA.

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19
Q

CH (Cheavy) affects the……but not the…..

A

biological functions but NOT antigen-binding specificity of the ab

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20
Q

Which does NOT contribute to Ig antigen-binding diversity

a. Any L chain can combine with any H
chain to form a functional antibody.

b. Any Vk can be joined to any Jk to encode the light chain V region.
c. Many CH genes are present in the germline DNA.
d. Random numbers of N nucleotides can be added during somatic recombination.
e. VJL and VDJH joining is imprecise.

A

c. Many CH genes are present in the germline DNA.

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21
Q

List 4 things that contribute to Ig ANTIGEN BINDING DIVERSITY

A

Any L chain can combine with any H
chain to form a functional antibody.

Any Vkappa can be joined to any Jkappa to encode the light chain V region.

Random numbers of N nucleotides can be added during somatic recombination.

VJL and VDJH joining is imprecise.

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22
Q

The proper joining of one VL to one JL is regulated by…..

A

12 and 23 nucleotide spacers between heptamer and nonamer sequences.

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23
Q

Clonal selection is the…..

A

availability of a mechanism to focus the antigen to the appropriate B cells and enable the stimulation of those B cells

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24
Q

Most cells of the vertebrate species have a diploid chromosomal organization and express both alleles of an active gene. The ….. are an exception to this rule because only ONE of their alleles is expressed as a FUNCTIONAL product.

A

Ig and TCR

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25
Q

Since each B cell productively rearranges a single H and L chain allele, it exhibits

a. affinity.
b. allelic exclusion
c. antibody restriction.
d. antigen-binding diversity.
e. cross-reactivity

A

b. allelic exclusion

Productively rearranging only one H and one L chain means that a single B cell makes antibodies with only one allotype and one antigen-binding specificity.

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26
Q

B cells must express an …..before they can mature and leave the marrow.

A

antigen receptor

where they travel to lymph nodes to meet antigens, and are activated go to the germinal centers and proliferate. Once they become plasma cells, they go back to the bone marrow.

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27
Q

Somatic recombination occurs

a. in the bone marrow stem cell.
b. in the progenitor cell as it is becoming a B cell.
c. in the mature B cell following antigen contact.
d. in the plasma cell after antigen contact.
e. in the plasma cell after antibody secretion.

A

b. in the progenitor cell as it is becoming a B cell.

the reason why its not a is because it said stem cell, stem cell which is incorrect

Somatic recombination occur prior to the B cell coming in contact with antigen, occurs in the bone marrow

once B cells have their BCR and are matured,naive B cells

they travel to the secondary lymphocytes and interact with their antigens and T helper cells, then they go to germinal centers to proliferate and differentiate

once they are plasma cells they return to their bone marrow

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28
Q

Plasma cells are effector cells and actually express little…..

A

MEMBRANE IG

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29
Q

Diversity comes from many different antigen-binding sequences; each B cell expresses

A

ONLY ONE

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30
Q

Cross-reactivity depends on

A

two antigens having similar epitopes, not on somatic recombination.

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31
Q

Isotype switching

a. changes the leader sequence exon so the antibody is secreted.
b. improves the antigen binding specificity of an Ig molecule.
c. increases the affinity of antibodies in a process called affinity maturation.
d. increases the functional diversity of Ig molecules.
e. occurs randomly between switch regions.

A

d. increases the functional diversity of Ig molecules.

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32
Q

Secretion versus membrane-bound Ig depends on which

A

CH exons are in the final message.

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33
Q

Different isotypes have different biological functions but they can have the same

A

antigen-binding specificity.

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34
Q

Isotype switching occurs at switch sites and is regulated by

A

helper T cell cytokines along with their cytokines to tell the B cell to secrete what kind of ab

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35
Q

Isotype switching resembles somatic recombination because both processes

a. are catalyzed by the products of RAG1 and RAG2
b. are regulated by helper T cell cytokines.
c. can result in stop codons in coding sequences.
d. occur in developing B cells in the bone marrow.
e. result in the irreversible loss of DNA from the B cell.

A

e. result in the irreversible loss of DNA from the B cell.

Both processed result in looping out of DNA.

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36
Q

Rag-1 and RAG-2 products catalyzes

A

antigen binding specificity

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37
Q

T cell cytokines do not…..

A

Regulated somatic recombination

since somatic recombination occurs prior to B cell meeting the antigen, engulfing, and presenting it as an APC for a T helper cell come along bind to it and secrete the necessary cytokines for the B cell differentiate into a plasma cell and start secreting high affinity antibodies

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38
Q

Splicing between gene segments is imprecise, sometimes resulting in nonproductive rearrangements in which

A

frame shift mutations yield stop codons downstream and no complete H or L chain can be produced.

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39
Q

Products of what genes are required for somatic recombination

A

two recombination-activating genes, RAG-1 and RAG-2

enzymes to ligate (reattach) the DNA

terminal deoxynucleotidyl transferase (TdT)

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40
Q

Junctional diversity affects primarily the amino acid sequence in

a. all CDR equally.
b. CDR1.
c. CDR2.
d. CDR3.
e. FR3.

A

d. CDR3.

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41
Q

Only ……..can be produced simultaneously. ………require isotype switching during which exons for mu and delta are lost. Select another answer.

A

IgM and IgD can be SIMULTANEOUSLY produced

IgG, IgA, and IgE need ISOTYPE SWITCHING

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42
Q

Alternative mRNA splicing occurs

A

> IMMATURE B CELLS

> IN BONE MARROW

> W/OUT T CELL HELP

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43
Q

.Alternative mRNA splicing

a. allows the B cell to improve its antigen-binding fit after antigen contact.
b. allows the B cell to make membrane IgM from the mature mRNA for secreted IgD.
c. can be used for the simultaneous production of any two Ig isotypes.
d. is a process by which a B cell can simultaneously synthesize m and d chains.
e. occurs in response to T cell cytokines.

A

d. is a process by which a B cell can simultaneously synthesize m and d chains.

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44
Q

Because of the order of the CH gene segments (Cm, Cd, Cg3, Cg1, pseudogene Ce, Ca1, Cg2, Cg4, Ce, and Ca2), a human B cell which undergoes isotype switching from IgM to IgG1 can never in the future secrete

a. IgA.
b. IgE.
c. IgG2.
d. IgG3.
e. IgG4.

A

d. IgG3.

The gamma 3 exon is upstream from gamma 1 and is lost in the isotype switch.

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45
Q

Gene recombination and DNA loss is part of isotype switching.

A

True

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46
Q

DNA between the former CH and the new CH is lost.

A

True

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47
Q

B cells can only produce…and… simultaneously.

A

IgM and IgD

via alternate splicing

other antibodies IgE, IgG, IgA have to undergo isotype switching

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48
Q

Isotype switching is always productive because

a. B cells produce all isotypes simultaneously.
b. isotype switching does not involve recombination of DNA gene segments.
c. no DNA is deleted from the chromosome in isotype switching.
d. no effector diversity results from isotype switching.
e. recombination between switch sites occurs in introns so it cannot introduce stop codons into coding regions.

A

e. recombination between switch sites occurs in introns so it cannot introduce stop codons into coding regions.

which is different from the VDJ/VJ variable binding regions where stop condons do occur in exons and results in a non-functional

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49
Q

Many B cells undergo unfavorable mutations and

A

die because they can no longer bind antigen.

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50
Q

Somatic hypermutation

A

1) occurs during B cell proliferatioin
2) occurs in B cell FOLLOWING antigen stimuation
3) result in increased affinity of ab secreted later in immune responses
4) result in death of some B cells which non longer bind antigen

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51
Q

Somatic hypermutation…. in the B cell which has bound antigen.

A

does occur

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52
Q
  • IMPORTANT

Somatic Recombination is NOT THE SAME AS somatic hypermutation in that.

A

> somatic recombination occurs PRIOR to antigen contact, during B cell development in BONE MARROW

> somatic HYPERMUTATION generates Ig diversity AFTER B cell has matured and migrated to the SECOND LYMPHOID ORGANS
- as B cells proliferate follwing antigen contact, mutations occur PREFERENTIALLY in VDJ, and VJ

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53
Q

In which of the following ways does the developmental pathway of α:β T cells differ from that of B cells? (Select all that apply.)

a. Their antigen receptors are derived from gene rearrangement processes.
b. When the first chain of the antigen receptor is produced it combines with a surrogate chain.
c. Cells bearing self-reactive antigen receptors undergo apoptosis.
d. MHC molecules are required to facilitate progression through the developmental pathway.
e. T cells do not rearrange their antigen-receptor genes in the bone marrow.

A

d. MHC molecules are required to facilitate progression through the developmental pathway.
e. T cells do not rearrange their antigen-receptor genes in the bone marrow.

they rearrange them in the THYMUS

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54
Q

Which of the following is the first stage of T-cell receptor gene rearrangement in α:β T cells?
a. Vα→Dα

b. Dα →Jα
c. Vβ→ Dβ
d. Dβ→Jβ
e. Vα→Jα.

A

d. Dβ→Jβ

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55
Q

______ of thymocytes is necessary to produce a T-cell repertoire capable of interacting with self-MHC molecules.

a. positive selection
b. negative selection
c. apoptosis
d. receptor editing
e. isotype switching.

A

a. positive selection

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56
Q

T-cell receptor binds strongly to self-peptides presented by self-MHC molecules,the thymocyte will be ……selected.

A

NEGATIVELY

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57
Q

T-cell who don’t recognize MHC molecules of the thymic epithelium will result in ….selection

A

POSTIVE

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58
Q

T-cell receptors may be autoreactive but escape ………..selection because its peptide antigen is ……..

A

NEGATIVE selection

its peptide antigen is present in tissues OTHER THAN THE THYMUS

59
Q

Thymocytes that are not positively selected

A

make up about 98% of developing thymocytes and die by apoptosis in the thymic cortex

60
Q

***All of the following types of protein are processed and presented by macrophages in the thymus except _____ proteins.

a. tissue-specific
b. soluble proteins from extracellular fluids
c. ubiquitous proteins
d. proteins made by macrophages
e. proteins derived from other cells that macrophages phagocytose

A

a. tissue-specific

this is important because thymocytes who are auto reactive to self peptides might escape negative selection if their self-tissue antigen isn’t present in the thymus

61
Q

The function of negative selection of thymocytes in the thymus is to eliminate

a. single-positive thymocytes
b. double-positive thymocytes
c. alloreactive thymocytes
d. autoreactive thymocytes
e. apoptotic thymocytes.

A

d. autoreactive thymocytes

62
Q

The human thymus begins to degenerate as early as one year after birth. This process is called______ and is marked by the accumulation of ___ once occupied by thymocytes.

a. thymectomy; dendritic cells
b. involution; fat
c. differentiation; γ:δ T cells
d. negative selection; γ:δ T cellse. involution; thymic stroma

A

b. involution; fat

63
Q

The human thymus begins to degenerate as early as one year after birth. This process is called______ and is marked by the accumulation of ___ once occupied by thymocytes.

a. thymectomy; dendritic cells
b. involution; fat
c. differentiation; γ:δ T cells
d. negative selection; γ:δ T cellse. involution; thymic stroma

A

b. involution; fat

64
Q

mature, naive B cells develop into Plasma cells in the

a. subendosteum
b. bone marrow
c. thymus
d. blood
e. secondary lymphoid organs.

A

e. secondary lymphoid organs.

65
Q

Place the following phases of a B cell’s life history in the correct chronological order.

a. negative selection
b. attacking infection
c. finding infection
d. searching for infection
e. repertoire assembly
f. positive selection.

A

repertoire assembly

negative selection

positive selection

searching for infection

finding infection

attacking infection

66
Q

Place the following stages of B-cell development in the correct chronological order.

a. early pro-B cell
b. large pre-B cell
c. immature B cell
d. stem cell
e. late pro-B cell
f. small pre-B cell.

A

stem cell >

early pro-B cell >

late pre-B cell >

large pre-B cell >

small pre-B cell>

immature B cell

67
Q

The consequence of allelic exclusion at the immunoglobulin loci ensures that _____.

A

B cells express antigen receptors of a SINGLE SPECIFICITY

homogeneous B-cell receptors bind more effectively to antigen

68
Q

Receptor editing occurs for B cells in the…….

A

bone marrow

to establish self tolerant repertoire

69
Q

List 4 properties of plasma cells

A

1) terminally differentiated B cells meaning they can’t divide anymore and are short lived
2) NO longer express MHC II
3) cease expressing membrane bound Ig
4) differentiate into plasma cells after migration from germinal center of lymphoid tissue and bone marrow

70
Q

Thymus independent antigen is…..as Thymus-dependent antigen

A

Thymus independent antigen is NOT as effective as Thymus Dependent

71
Q

IgM is the…. after antigen exposure

A

First ig

72
Q

IgM

A

1) PENTMAERIC in SECRETED form
2) stays in serum, too large to go to tissue
3) ANTIBACTERICIDAL, complement-binding antibody
4) RA autoantibody of IgG’s Fc
5) MONOMERIC in MEMBMRANE form
6) first antibody produced ruing intial exposure to antigen, primary response

transiently expressed after infection therefore ordering lab tests for IgM is a good idea after a recent exposure to pathogen

to test it pt has immunity for a certain pathogen, use IgG which remains in serum months and years after exposure. placenta also

IgA is to test for mucosal immunity in GI tract, Airways, and Lungs since its in secretion, IgA can exist as a dimer in secretions

IgE is for allergic reactions, inducing mast cells to release granules, or parasitic infections.

73
Q

IgG

A

1) Major isotype of circulating serum antibody, longest half life
2) ONLY isotype to cross placenta
3) fixes complement, acts as OPSONIN
4) stimulates chemotaxis

74
Q

IgA

A

1) predominant antibody on EXTERNAL SECRETIONS (saliva, mucus, breast milk)
2) mono mostly in serum and DIMER in secretion
3) PREVENTS adherence of microbes to mucus membranes

75
Q

IgE

A

1) TYPE I IMMEDIATE hypersensitivity
2) Antiparasitic
3) Binds tightly to Fc receptor on Mast cells

76
Q

All antibodies produced by an individual B cell have the same antigenic specificity

A

True

77
Q

Light chain gene has

A

VJC segments

either get JVC recombination on KAPPA

or

either get JVC recombination on LAMBDA

78
Q

Heavy chain gene has

A

VDJC segments

79
Q

B cells require …… to respond to most antigens

A

T HELPER Cells and CYTOKINES

80
Q

For T dependent stimulation, describe the costimulatory signal

A

T helper’s cell’s CD40L bind to CD40 on B cells promotes increased expression of cytokine receptors on B cell

81
Q

For T dependent stimulation, coreceptors….and…instensify initial signal triggered by antigen binding

A

CD21 and CD19 on B cell

82
Q

For T dependent stimualtion, describe cytokine signals

A

B cell differentiate after binding to cytokines secreted by T H cells

plasma cells are terminally differentiate B cell that SECRETE antibody

Memory B cells which express MEMBRANE bound ab of any isotype respond FASTER than naive B cells to second exposure to antigen

83
Q

Antibody effector mechanisms List 3

1) Neutralization of viruses and toxins
when agents become coated with ab, which intereferes with their binding to receptors,preventing infectious/toxic process from proceedding

2) opsonization IgG
promotes ingestion and killing by phagocytic cells

3)Complement Activation IgG and IgM
induces inflammatory response and cytolytic destruction of extracellular microbes

A

1) Neutralization of viruses and toxins

when agents become coated with ab, which intereferes with their binding to receptors,preventing infectious/toxic process from proceedding

2) opsonization IgG

promotes ingestion and killing by phagocytic cells

3)Complement Activation IgG and IgM

induces inflammatory response and cytolytic destruction of extracellular microbes

84
Q

Explain the difference b/w BCR and antibodies

A

C terminus of the HEAVY CHAIN for BCR is HYDROPHOBIC

C terminus for the HEAVY CHAIN ab is HYDROPHILLIC

85
Q

Light Chain has ……but a single immunoglobulin uses only……

A

Light Chain has lambda or kappa but a single immunoglobulin uses only lambda OR kappa, NOT BOTH

On lambda light chain genes, there’s V and J and C

On KAPPA light chains, there’s V, J, and C

86
Q

***Papin digestion celaves antibody into

A

two FAB fragments and ONE Fc fragment

87
Q

Pepsin digestion celaves ab into

A

Separates the FAB fragments from the Fc fragments, but the FAB fragments are still bound together even after the seperation

88
Q

Hypervariable regions of ig and TCR corresponds to….

A

antigen-binding regions

89
Q

*****Antibodies antigens can be anything that can bind anywhere on the antibody’s variable region (doesn’t have to be the pocket like MHC) and they don’t even have to be peptides.

A

True

90
Q

Antibodies recognize both

A

1) specific sequences

2) structural shape

91
Q

how do antigens bind ig?

A

1) electrostatic forces (positive charge with negative charge)
2) hydrogen bonds
3) van der waals
4) hydrophobic forces, hydrophobic molecules pack together in unfavorable water environment also involves van der waals

92
Q

Describe how somatic recombination (not somatic hypermutation which occurs after antigen and t cell meet with b cell) works….

A

1) RAG binds and cleaves to yield a DNA hairpin
2) RAG cleaves the hairpain to generate PALINDROMIC P-nucleotides (two strands bind to each other but if read them the same direction they are identitical)
3) N-nulceotide additions by Tdt
4) pairing of strands
5) unpaired nucleotides are removed by exonulcease
6) gaps gaps are filled by DNA synthesis and ligation to form coding joint

93
Q

Somatic hypermutation is specific to the

A

1) Ig sequences and not for other genes in the same activated B cell
2) increases following B cell activation and is assoc with B cell proliferation events

94
Q

Early pro B-cell

A

DJ rearranging on H chain

95
Q

Late pro B-cell

A

V-DJ rearranging on H chain

96
Q

Large pre-B cell

A

VDJ arranged

mu chain transiently at surface as part of pre-B cell receptor mainly intracelluar

97
Q

Small pre-B cell

A

V-J rearranging in L chain

itracellular mu chain

98
Q

Immature B cell

A

VDJ rearranged
VJ rearranged

IgM expressed on cell surface

NOT YET for IgD, this happens in MATURE naive B cells

99
Q

***Mature B cell

A

IgD and igM made from alternatively spliced H chain transcripts

100
Q

Generation of B cell receptors occur in

A

the BONE MARROW

101
Q

Negative selection of B cells occurs in the

A

BONE MARROW

102
Q

Which antibody is generally lower affinity than later isotypes?

A

IgM

103
Q

Which two antibodies can form multiplers?

A

IgM as a pentamer in serum

IgA as a dimer in secretions

104
Q

Avidity

A

Total binding strength

105
Q

Why do antibodies polymerize?

A

Binding of repetitive epitopes increases avidity (total binding strength) which partially offsets/compensates for lower affinity

THEY COMPENSATE FOR THEIR LOWER AFFINITY WITH AVIDITY BY POLYMERIZING

I”M LOOKING AT YOU IGM

106
Q

How do IgM get around being lower affinity than other antibodies?

A

It increases its avidity, binding strength by polymerizing so it can bind repetitive epitotoes which increases its avidity and offsetting its lower affinity

107
Q

Are the first isotype(s) generated and are alternate spliced products of the same immature RNA transript transcribed from a single gene

A

IgM and IgD

108
Q

Which Isotypes are generated by isotype switching

A

IgG, IgE, IgA

109
Q

mature, Naive B cells express

A

IgM and IgD

110
Q

When B Cells are activated they cease to express….

A

IgD

and

initially produce and secrete SERUM IgM

111
Q

IgM was switched to IgE from cytokine signals do they still recognize the same antigen epitope?

A

yes, isotype switching does not affect antigen binding variable region

the ag:ab now triggers a DIFFERENT FUNCTION via the new constant region

112
Q

B cells can undergo isotype switching….following additional activation

A

MORE THAN ONCE

113
Q

When VDJ is moved to constant region gamma the b cell makes

A

IgG

114
Q

WHen VDJ is moved to constant region alpha, the b cell makes

A

IgA

115
Q

V region assembly

what is the process:

is it reversible/irreversible?

Does it occur on B cells

Does it occur on T cells

A

V region assembly

SOMATIC recombination (NOT SOMATIC HYPERMUTATION WHICH ONLY OCCURS IN B CELLS)

IRREversible

B Cell YES

T Cells Yes

116
Q

Junctional Diversity

process

reversible/irreversible

Does it occur on B cells

Does it occur on T cells

A

Junctional Diversity

IMPRECISE joining, N-sequence insertion in DNA (joining of alpha to beta or, light chain to heavy chain)

IRREversible

B cells YES

T cells YES

117
Q

Transcriptional Activation

process

reversible/irreversible

B cells?

T cells?

A

Transcriptional Activation

ACTIVATION of PROMOTER by proxmimity to the enhancer

B cells YES

T cells YES

118
Q

VERY IMPORTANT

hypermutation does it occur in both B cell and T cell?

A

NONONONONONO!!!!!

Somatic HYPERmutation occurs ONLY IN B CELL

119
Q

Is IgM and IgD expression on surface reversible or irreversible?

A

Reversible

DIfferential splicing of RNA

120
Q

Is Membrane vs secreted form for Ig reversible or irreversible?

A

Reversible

Differntial splicing of RNA

121
Q

**Cytokine expression regulates antibody…..

A

isotype switching

122
Q

Where do activated B cells proliferate?

A

In the lymph nodes, specificallythe GERMINAL ZONES in spleen, lymph nodes, or inflammation sites

123
Q

When B cells differentiate into plasma they go to the….

A

BONE MARROW

124
Q

When do B cells express MHC II?

A

when it is resting B cell (doesn’t secrete Ig)

or 
as  PLASMABLAST (secretes Ig)
125
Q

Do plasma cells have MHC II?

A

No

126
Q

When can B cells undergo somatic hypermutation and increase ab affinity?

A

1) naive Resting b cell

or

2) MEMORY B cell

NEVER PLASMA B CELL, since its already become a antibody secreting factory, it cannot under go somatic hypermutation as it is a irreversible process and the plasma b cell has already gone through that

127
Q

When can B cells still Isotype switch?

A

As a resting B cell, or Palsmablast

UNTIL IT CAN NO LONGER receive help from CD4 helper T cell, when it expresses MHC II

128
Q

When do B cell not need CD4 T cell helper?

A

Plasma Cell

which are cell dedicated to secreting ab

1) does NOT have MHC II
2) cannot undergo somatic hypermutatoin
3) cannot isotype switch

129
Q

Explain the difference between Th1 and Th2 CD4 cells

A

both are T helper cell

Th1 is involved in

1) macrophage activation
2) IgG secretion, IgG SECRETION, IgG SECRETION!!!!!!!
3) autoimmune disorders

Th2 is involved in

1) Mast Cell activation
2) Eosinophil activation
3) Allergic Reactions
4) parasites

130
Q

B cells secreting IgE need which type of T cell?

A

1) Helper T cell

2) Helper 2 T cell, since IgE is involved in allergic rxn

131
Q

What affects T helper cells differentiation into either Th1 or Th2?

A

1) Density of MHC II receptors for the T helper’s corresponding APC

APC has high density MHC II
TH1 is developed

APC has low density MHC II
TH2 is developed

why did I only write MHC II here and not the other MHC, because APC has MHC II

2) type of APC and co-stimulatory elements encounter by CD4 helper cell
3) Cytokine environment

IL4 and IL5 induces Th2 differentiation

132
Q

Which cytokines induces Th2 differntiation?

A

IL4 and IL5

133
Q

An APC has high density of MHC II being presented to CD4 T cell, which helper cell does it differntiates to?

A

Th1 helper CD4 T cell

134
Q

APC presents peptide with weak binding to the T cell receptor, T cell differentiatates into a?

A

TH2 Cell

135
Q

Apc presents peptide with STRONG binding to T cell receptor, T cell differentiates into a?

A

Th1 cell

136
Q

Factors produced by Th1 and Th2 negatively cross regulate each other meaning that they?

A

Factors secreted by Th1 INHIBITS DIFFERENTIATION of Th2, and vice versa

137
Q

Is helpful in diagnosing,….recent infections?

A

transient presence of IgM ab is helpful in dx RECENT infections

since other ab are higher affinity than IgM, IgM isn’t secreted any more when b cell meets its antigen, corresponding helper T cell, and receives cytokines from T cell to undergo isotype switching for a more higher affinity Ig

Recent infection will show IgM in blood serum, since IgM is first initially expressed before the B cell undergoes isotype switching to secrete a more specific antibody than a generalist IgM

138
Q

You recently participated in a chicken pox party, your doctor orders both IgG and IgM test?

A

IgM to determine if there was a recent infection

IgG to see if you’ve built long lasting immunity

IgA is important for mucosal immunity

139
Q

When you ask your doctor to test if you’re immune to certain pathogens and you’ve told him you’ve had vaccines before, why is it only necessary for him to check IgG?

A

IgG is ordered to see if you’ve build long lasting immunity

since

IgG remains detectable for months or YEARS

IgM become UNDETECTABLE following weeks/months after infection, its only useful to figure out if you’ve had a recent infection

140
Q

IgG antibodies

A

1) inactivate toxins
2) opsonize bacteria
3) activate COMPLEMENT
3) neutrallize viruses and bacteria that CROSS THE PLACENTA

141
Q

IgA are important in which body parts

A

mucosal immunity in the

1) GI tract
2) Nose
3) Lung

142
Q

IgE fight

A

1) parasite
2) worms
3) CAUSES ALLERGIC RXN via activating MAST CELLS

143
Q

Which antibody is really important in protecting the conceptus from viruses and bacteria across the placenta?

A

IgG

144
Q

B cells must be first activated by their….before they can go to the germinal centers in lymph node and proliferate and differentiate into plasma cells

A

antigens and T helper cells

Immune week 6 (8 decks)

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