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

Lecture 6 Flashcards

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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
Q

Where does signal 2 come from in thymus dependent antigens?

A

Signal 2 is provided by CD4+ T cells

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26
Q

What is TI?

A

It is a complex protein which has different components and has a receptor on its antigen which the B cell recognises

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27
Q

What happens in TD?

A

The antigen binds to the b cells giving signal 1 but it also needs signal 2

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28
Q

How is signal 2 found in TD?

A

Through MHC class II, the B cell will take a peptide from the MHC class II onto its surface and this produces signal 2

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29
Q

How is signal 2 found on TI?

A

Delivered by the thymus independent antigen

30
Q

What are the two types of TI-antigens?

A

TI-1 and TI-2

31
Q

What do TI antigens do?

A

Induce antibodies in absence of T cells

32
Q

What antibody is produced from TI antigens?

A

Only IgM

33
Q

What happens in high concentrations to the antigens?

A

They act as polyclonal activators for B cells

34
Q

What does polyclonal activators mean?

A

The antigens will activate many B cells irrespective of their different BCR

35
Q

What are the two signals from in TI-1?

A

Signal 1 = BCR signal 2 = from TLR

36
Q

What structure is TI-2?

A

A polysaccharide, has repeating structures so it can bind to lots of different BCRs on the surface

37
Q

What are TI-2 important in?

A

Bacterial infections

38
Q

What do TI-2 do to BCR molecules?

A

Cross link BCR on the same B cell surface

39
Q

How long does it take for TI-2 antigens antibody responses to develop?

A

More than 5 years

40
Q

What signals are seen in TI-2?

A

Only signal 1 or a strong signal 1

41
Q

What are the antibody responses like in TD compared to TI?

A

They are much better

42
Q

How is signal 2 carried out in a TD antigen?

A

Is from the T cell but need a CD40 ligand interaction to cytokines

43
Q

What do cytokines secreted by the T cells do?

A

Drive class switching

44
Q

What do IgM and IgD switch to?

A

IgG and IgA

45
Q

How are epitopes joined?

A

Physically joined together by viral particles, protein and a sugar

46
Q

What happens when converting a TI antigen to a TD antigen?

A

Makes a conjugate vaccine

47
Q

What is an example of a conjugate vaccine?

A

Haemophilias influenza type b

48
Q

What is the TI antigen in influenza type b vaccine?

A

Protective responses capsular polysaccharide

49
Q

What is the TD in the influenza type b vaccine?

A

Protein tetanus toxoid

50
Q

When can you get a conjugate vaccine?

A

5 years and older

51
Q

What happens if the antigen is TD?

A

B cell presents peptides from Ag to CD4+Thelper cells

52
Q

What do the CD4+Thelper cells form in the lymph node?

A

B/T cell conjugate

53
Q

How do activation induced deaminase (AID) get induced?

A

By CD40 signal

54
Q

What does AID induce?

A

Somatic hypertension in b cells

55
Q

What hypermuates in the B cells?

A

The V,D,J segments

56
Q

What are germinal centres?

A

Proliferating B cells

57
Q

What do the b cells divide into in the germinal centres?

A

Centroblasts

58
Q

What happens inside the centroblasts?

A

Hypermutation and class switching

59
Q

What happens after centroblasts?

A

Turn into a non dividing state called a centrocytes

60
Q

What is the process states of a B cell?

A
  1. B cell
  2. Centroblasts
  3. Centocytes
61
Q

What is the dark zone?

A

Loads of proliferating cells

62
Q

How is signal 3 delivered?

A

By antigen-presenting cells

63
Q

What happens to B cells in a germinal centre? - 3 ways

A

Differentiate into plasma cells, form long lived memory cells or die within the lymphoid

64
Q

What is somatic hypermuation?

A

Randomly mutate the DNA at the V,D,J regions

65
Q

What are also present in the GC (germinal centre)?

A

Follicular dendritic cells and antigens

66
Q

What do follicular dendritic cells do?

A

Display the antigens to the b cells

67
Q

What do centrocytes do?

A

Compete with each other for an antigen

68
Q

What are follicular T helper cells?

A

Help B cells

69
Q

Where to Thelper cells Come from,?

A

CD4+Th

70
Q

What is the role of CD40?

A

Projects centrocytes from apoptosis

71
Q

What does CD40 a signal induce?

A

Class switching

72
Q

What cytokine is needed for IgE class switching?

A

IL-4

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

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