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Cell And Molecular Biology Of The Immune System > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

What induces clonal deletion?

A

If B cells recognise self antigens

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2
Q

How many BCR are on each B cell surface?

A

1 - each b cells has a different BCR

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3
Q

How can B cells escape death?

A

By replacing the light chain with another one

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4
Q

When can RAG genes make a new light chain?

A

If the flight light chain is autoreactive

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5
Q

What are the 3 antibody functions?

A

Neutralisation, opsionisation and complement activation

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6
Q

What is Antibody neutralisation?

A

Antibody prevents bacterial adherence

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7
Q

What is antibody opsonisation?

A

Antibody promotes phagocytosis

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8
Q

What is antibody complement activation?

A

Antibody activates complement which enhances opsonisation and lyses some bacteria

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9
Q

What is found at the constant?

A

IgM and IgD

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10
Q

What is special about a BCR?

A

It only recognises one antigen

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11
Q

Where will the b cells look to find an antigen?

A

In the lymphatics and blood

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12
Q

What produces signal 1?

A

Binding of an antigen to a BCR

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13
Q

What activates intracellular kinases?

A

Cross linking BCR

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14
Q

What does kinases being activated lead to?

A

Transcription factors and gene expression

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15
Q

What types of motifs does the CD3 complex contain?

A

ITAM motifs

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16
Q

What do kinases phosphorylate?

A

Tyrosines

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17
Q

What makes signal 1 stronger?

A

Complement receptors

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18
Q

What is an example of a complement receptor?

A

CR2

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19
Q

What happens if the antigen that binds BCR is coated with C?

A

It can also bind CR2 on b cells and give an increased signal

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20
Q

What does signal 2 depend on?

A

Depends on the type of antigen that the B cell is recognising

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21
Q

Where does signal 2 come from in thymus independent antigens?

A

Antigen or cross linking of BCR

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22
Q

What are the two types of antigens that can move to trigger a B cell response?

A

Thymus independent and thymus dependent

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23
Q

What is a thymus independent antigen?

A

Can get a response to an antigen without the use of T cells, can get a B cell response in an antigen where you’ve taken the thymus out

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24
Q

What is thymus dependent?

A

Need T cells in order for a B cell response, do not get a B cell response in the absence of a thymus

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25
Where does signal 2 come from in thymus dependent antigens?
Signal 2 is provided by CD4+ T cells
26
What is TI?
It is a complex protein which has different components and has a receptor on its antigen which the B cell recognises
27
What happens in TD?
The antigen binds to the b cells giving signal 1 but it also needs signal 2
28
How is signal 2 found in TD?
Through MHC class II, the B cell will take a peptide from the MHC class II onto its surface and this produces signal 2
29
How is signal 2 found on TI?
Delivered by the thymus independent antigen
30
What are the two types of TI-antigens?
TI-1 and TI-2
31
What do TI antigens do?
Induce antibodies in absence of T cells
32
What antibody is produced from TI antigens?
Only IgM
33
What happens in high concentrations to the antigens?
They act as polyclonal activators for B cells
34
What does polyclonal activators mean?
The antigens will activate many B cells irrespective of their different BCR
35
What are the two signals from in TI-1?
Signal 1 = BCR signal 2 = from TLR
36
What structure is TI-2?
A polysaccharide, has repeating structures so it can bind to lots of different BCRs on the surface
37
What are TI-2 important in?
Bacterial infections
38
What do TI-2 do to BCR molecules?
Cross link BCR on the same B cell surface
39
How long does it take for TI-2 antigens antibody responses to develop?
More than 5 years
40
What signals are seen in TI-2?
Only signal 1 or a strong signal 1
41
What are the antibody responses like in TD compared to TI?
They are much better
42
How is signal 2 carried out in a TD antigen?
Is from the T cell but need a CD40 ligand interaction to cytokines
43
What do cytokines secreted by the T cells do?
Drive class switching
44
What do IgM and IgD switch to?
IgG and IgA
45
How are epitopes joined?
Physically joined together by viral particles, protein and a sugar
46
What happens when converting a TI antigen to a TD antigen?
Makes a conjugate vaccine
47
What is an example of a conjugate vaccine?
Haemophilias influenza type b
48
What is the TI antigen in influenza type b vaccine?
Protective responses capsular polysaccharide
49
What is the TD in the influenza type b vaccine?
Protein tetanus toxoid
50
When can you get a conjugate vaccine?
5 years and older
51
What happens if the antigen is TD?
B cell presents peptides from Ag to CD4+Thelper cells
52
What do the CD4+Thelper cells form in the lymph node?
B/T cell conjugate
53
How do activation induced deaminase (AID) get induced?
By CD40 signal
54
What does AID induce?
Somatic hypertension in b cells
55
What hypermuates in the B cells?
The V,D,J segments
56
What are germinal centres?
Proliferating B cells
57
What do the b cells divide into in the germinal centres?
Centroblasts
58
What happens inside the centroblasts?
Hypermutation and class switching
59
What happens after centroblasts?
Turn into a non dividing state called a centrocytes
60
What is the process states of a B cell?
1. B cell 2. Centroblasts 3. Centocytes
61
What is the dark zone?
Loads of proliferating cells
62
How is signal 3 delivered?
By antigen-presenting cells
63
What happens to B cells in a germinal centre? - 3 ways
Differentiate into plasma cells, form long lived memory cells or die within the lymphoid
64
What is somatic hypermuation?
Randomly mutate the DNA at the V,D,J regions
65
What are also present in the GC (germinal centre)?
Follicular dendritic cells and antigens
66
What do follicular dendritic cells do?
Display the antigens to the b cells
67
What do centrocytes do?
Compete with each other for an antigen
68
What are follicular T helper cells?
Help B cells
69
Where to Thelper cells Come from,?
CD4+Th
70
What is the role of CD40?
Projects centrocytes from apoptosis
71
What does CD40 a signal induce?
Class switching
72
What cytokine is needed for IgE class switching?
IL-4

Cell And Molecular Biology Of The Immune System (12 decks)

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