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B cell maturation Flashcards

1
Q

what kind of receptor do B cells express

A

B cell receptor (BCR)

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2
Q

how does BCR recognize antigen

A

via membrane Ig

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3
Q

T/F the BCR on each B cell clone is specific for a distinct antigen

A

True

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4
Q

what are the five Ig types

A

IgG, IgE, IgM, IgA, IgD

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5
Q

Ig isotype is based on what

A

heavy chain

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6
Q

which Ig(‘s) is/are monomeric with 2 binding sites

A

IgD, IgE, IgG

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7
Q

which Ig(‘s) is/are pentamers with 10 binding sites

A

IgM

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8
Q

which Ig(‘s) is/are dimers with 4 binding sites

A

IgA

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9
Q

Ig are Y shaped molecules formed by:

A

two heavy chains and two light chains

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10
Q

what does the light chain consist of

A

1 variable domain and 1 constant domain

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11
Q

what does the heavy chain consist of

A

1 variable domain and 3 or 4 constant domains

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12
Q

what are the two forms that Ig can exist in

A

membrane-bound or secreted

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13
Q

which region contains the antigen binding site

A

variable regions

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14
Q

which region mediates the effector function? and what are those funcitons?

A

constant region.
- determines isotype
- bind complement
- bind Fc receptors

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15
Q

how many bind sites are there per Y structue

A

2

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16
Q

does variable chain bind wide variety of antigen or a very specific type of antigen

A

wide variety (in contrast with T cells):
- proteins
- lipids
- polysaccharides
- nucleic acid

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17
Q

does variable chain recognize processed or non-processed antigen

A

native not processed antigen is recognized
(in contrast with T cell receptor which recognizes processed peptide)

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18
Q

what is the antigen part recognized by antibody

A

epitope

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19
Q

which is the first C region cluster

A

Cu (greek letter mu)

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20
Q

which is the first antibody to be produced

A

IgM

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21
Q

during recombination of Ig genes, is it randomly selected or precisely selected?

A

random

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22
Q

what is the random recombination mediated by

A

RAG specific for VDJ
- brings two segments close together

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23
Q

how else is diversity generated for Ig

A

exonucleases and Tdt

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24
Q

where does B cell positive selection occur

A

bone marrow

25
is positive selection for B cells antigen dependent or independent
antigen independent
26
what are the two checkpoints in B cell maturation
preBCR and IgM
27
T/F B cell needs either preBCR or IgM to promote survival
False. It needs both preBCR and IgM
28
what is negative selection for B cells
eliminate B cells that can bind with high affinity ubiquitous self antigens
29
what else can a B cell do instead of dying that results in change of the Ig specificity
Receptor editing
30
what do plasma cells produce
high affinity Ig
31
where do plasma cells migrate to and how long do they survive
Bone marrow or mucosal tissues survive for years
32
do memory B cells secrete Ig
nope
33
how long do memory B cells survive and where
a lifetime in mucosal tissues and blood
34
compare secondary antibody response to primary antibody response in terms of 1. response time 2. response amount 3. antibody type 4. antibody affinity
Primary: slower, smaller, IgM > IgG, low affinity Secondary: quicker, larger, IgG more abundant, high affinity
35
what are two to enhance B cell activation
1. simultaneous engagement of antigen receptor (BCR) and CR2 2. TLR
36
what delivers the CR2 activating signal
CD19 and CD81
37
what are the two types of antibody responses
T dependent response and T independent response
38
for the T dependent response, what kind of antigen, what Ig, and what kind of affinity?
- protein antigen (T cells only recognize protein antigens) - isotype switching - high affinity Ig
39
for the T independent response, what kind of antigen, what Ig, and what kind of affinity?
- nonprotein antigen - IgM - low affinity Ig
40
define a hapten
small molecule that cannot elicit an immune response by themselves but do so after bind to larger proteins or cells
41
what are the steps of T-B cell interaction and antibody responses?
1. simultaneous activation of T and B cells by antigen in T cell zone and follicle, respectively 2. migration towards each other 3. B cells migrate back to follicles where germinal center rnx occurs
42
which chemokine is for T cells to go to T cell zone
CCR7
43
which chemokine is for B cells to go to B cell zone (follicle)
CXCR5
44
during antigen presentation by B cells to T helper cells, which cell processes the antigen
B cells
45
T/F B cells and T cells recognize different epitopes of the same protein
True
46
which protein epitope do B cells recognize
native conformational epitope
47
which protein epitope do T cells recognize
peptide fragments
48
when T cell recognizes peptide presented to it by the B cell, what does this induce
CD40L upregulation in T cells and production of cytokines
49
in the B and T cell interaction, where is CD40 present and where is CD40L present?
CD40 on B cells CD40L on T cells
50
what does engagement of CD40 and cytokine receptor on B cells lead to
proliferation and differentiation in plasma cells
51
what 3 things happen in the germinal center
isotype switching affinity maturation selection of high-affinity B cells
52
what is isotype switching
change in the C region of the heavy chain with no change in specificity (recognition of antigen doesn't change)
53
what does isotype switching require
CD40L signal from Tfh (T follicular helper cells)
54
the type of heavy chain isotype is determined by what
cytokines produced by Tfh cells (IgG and IgE) or tissues (IgA)
55
what happens during switch recombination
the VDJ exon is brought next to a different C gene
56
T/F during switch recombination the specificity of the Ig does not change, while the C region is different and reflected the function of the Ig
True
57
what is affinity maturation
point mutation in the V regions - selection of B cells with high-affinity antigen receptors
58
during selection of high-affinity B cells, what interactions promote their survival
interactions with follicular DC that display antigen and Tfh cells
59
T/F B cells compete for antigen and those with low affinity for antigen will survive
False. those with high affinity will survive

Micro (15 decks)

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