adaptive immunity Flashcards

1
Q

what is adaptive immunity consist of?

A

cell mediated responses and antibody (humoral) responses

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2
Q

adaptive immunity is carried out by which two cells?

A

B and T cells

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3
Q

which cell drives cell-mediated immunity?

A

T cell

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4
Q

cell-mediated immunity involves the activation of which cells?

A

macrophages, NK cells ad antigen-specific cytotoxic T cells

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5
Q

what is the key feature of adaptive immunity?

A

immunological memory - each pathogen is remembered by signature T cell or B cell receptor

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6
Q

how does adaptive immunity differ from innate in the number of genes required?

A

adaptive immunity requires several where as innate requires 1

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7
Q

name the 3 receptors involved in adaptive immunity?

A
  • T cell receptor (TCR)
  • B cell receptor (immunoglobulin [IgA])
  • major histocompatibility complex (MHC protein)
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8
Q

T cells can be classified into two types, what are these?

A
  • CD4+

- CD8+

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9
Q

which type of T cells are CD4+?

A

helper T cells

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10
Q

which type of T cells are CD8+?

A

Cytotoxic T cells

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11
Q

what is the CD antigen on T cells?

A

a cluster of differentiation cell surface markers involved in signalling

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12
Q

what are the 2 types of MHC molecules?

A

MHC class i and MHC class ii

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13
Q

what are MHC molecules?

A

cell surface markers involve din signalling

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14
Q

which cells contain MHC class i on their surface?

A

all nucleated cells

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15
Q

which cells contain MHC class ii on their surface?

A

antigen presenting cells, dendritic cells, macrophages, and B cells

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16
Q

CD4+ helps signalling through which molecule?

A

MHC class ii

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17
Q

CD8+ helps signalling through which molecule?

A

MHC class i

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18
Q

when CD is seen alone, it refers to which type of T cell?

A

CD8+ (cytotoxic)

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19
Q

what co-receptor is involved in the binding/activation to MHC class i?

A

CD8+

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20
Q

what co-receptor is involved in the binding/activation to MHC class ii?

A

CD4+

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21
Q

what co-receptor is involved in the binding/activation of both CD4+ and CD8+ T cells?

A

CD3

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22
Q

what are the 2 structural classes of T cell receptors?

A

alpha-beta T cells (most common) and gamma-delta T cells

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23
Q

describe the structure of a T cell receptor?

A
  • can have either an alpha and beta chain or a gamma and delta chain
  • has constant and variable region
  • transmembrane region
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24
Q

which region of a T cell receptor determines variable binding?

A

variable region

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25
Q

how many gene segments encode the variable region of the alpha chain of a T cell receptor?

A

2 gene segments

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26
Q

how many gene segments encode the variable region of the Beta chain of a T cell receptor?

A

3 gene segments

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27
Q

which gene segments encode the variable region of the alpha chain?

A
  • V (variable)

- J (joining)

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28
Q

which gene segments encode the variable region of the Beta chain?

A
  • V (variable)
  • J (joining)
  • D (diversity)
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29
Q

where do B cells mature?

A

bone marrow

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30
Q

where are B cells found?

A

largely in lymphoid organs, also circulating blood and lymph

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31
Q

B cells recognise antigens through which molecule?

A

BCR

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32
Q

The B cell receptor is actually what immunological molecule?

A

the antibody

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33
Q

what happens to B cells once they are activated?

A

turn into plasma cells and churn out lots of antibodies against specific pathogens

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34
Q

what is another term for antibodies?

A

immunoglobulins

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35
Q

describe the structure of an immunoglobulin?

A
  • 2 chains: heavy and light
  • constant (bottom) and variable (top) region
  • Y shape
  • flexibility round tail
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36
Q

what are the 5 classes of antibodies?

A
  • IgG
  • IgE
  • IgD
  • IgM
  • IgA
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37
Q

what is the main function of an antibody?

A

prevent microorganism adhesion, activation of complement, neutralise toxin, opsonisation to promote phagocytosis and destruction

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38
Q

heavy chain region of immunoglobulin involve the rearrangement of which gene segments?

A
  • V (variable)
  • D (diversity)
  • J (joining)
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39
Q

light chain region of immunoglobulin involve the rearrangement of which gene segments?

A
  • V (variable)

- J (joining)

40
Q

immature BCRs are usually which antibody?

A

IgM

41
Q

which cells, B or T, undergo only negative selection?

A

B cells

42
Q

what occurs during negative section of B cells?

A

B cells are show lots of self antigens to see if they respond, ensures no reactivity against self antigens

43
Q

antibodies consist of light & heavy chains which come together to create which two regions?

A

FAB (fragment-antigen-binding) antigen binding region and Fc (tail) region which binds to cellular receptors and complement

44
Q

which two classes of antibody are BCRs?

A

IgM and IgD

45
Q

how is diversity of antibody specificity generated?

A

gene re-arrangement during development

46
Q

B cell activation can occur dependant or independent of which molecule?

A

T cell

47
Q

what determines whether a B cell requires T cell activation?

A

the type of antigen presented on the B cell

48
Q

antigens on the B cell requiring T cell help are called?

A

thymus-dependant antigens (TD)

49
Q

antigens on the B cell not requiring T cell help are called

A

thymus-independent antigens (TI)

50
Q

where does B cell activation mainly occur?

A

lymphoid organs

51
Q

some B cell activation occurs the periphery, which type of activation is this?

A

thymus independent

52
Q

activation naive B cells produces which type of cell?

A

plasma cell

53
Q

if a B cell requires T cell activation, this usually occurs where?

A

lymph node

54
Q

B cells producing which antibodies don’t need T cell help during activation?

A

B cells producing IgA or IgD

55
Q

B cells producing which antibodies need T cell help during activation?

A

B cells producing IgM or IgG

56
Q

interaction between B and T cells requires the binding of which co-receptor to which ligand?

A

CD40 to CD40L

57
Q

before undergoing class switching, B cells normally express which antibody?

A

IgM

58
Q

which antibody id more effective, IgM or IgG?

A

IgG

59
Q

the second immunological response is said to have higher?

A

affinity and avidity

60
Q

what is affinity?

A

strength of binding of single antibody to antigen

61
Q

What is avidity?

A

ability of antibodies to form complexes

62
Q

IgM response is weak so antibodies change class to IgG/A/E, this occurs by?

A

gene rearrangement (antibody binding site remains the same)

63
Q

certain antigens can active B cells directly without the need for a T cell, give an example of one of these antigens?

A

bacterial LPS

64
Q

does thymus independent B cell activation produce memory cells?

A

no

65
Q

what is the primary immune response?

A
  • primary exposure to antigen leads to development of immunological memory which takes time
  • IgM acts early on before class switching
66
Q

what is the secondary immune response?

A
  • due to generation of memory T and B cells, we already have a pool of cells waiting to respond immediately
  • cells are also primed to produce a more effective IgG (rather than IgM)
67
Q

what is immunological tolerance?

A

state of immune unresponsiveness to a particular antigen or set of antigens

68
Q

which tolerance, B cell or T cell is more important and why?

A

T cell tolerance is more important- b cells cannot make antibodies without the help of T cells

69
Q

what are the 2 types of immune tolerance?

A
  • central

- peripheral

70
Q

what is central tolerance?

A

occurs while developing immune cells are still present in primary lymphoid organs, prior to exportation to periphery

71
Q

what is peripheral tolersance?

A

occurs outwit thymus and bone marrow

72
Q

central T cell tolerance is referred to as what?

A

thymus education

73
Q

is T cell central tolerance 100% effective?

A

no - 10% of self reacting T cells remain after

74
Q

describe the process of central T cell tolerance?

A
  • T cells must bind with the correct strength to MHC molecules, those that do survive positive selection
  • T cells must not bind to self antigens, those that do are elevated by negative selection
  • rest of T cells emigrate to peripheral tissue and lymphoid organs
75
Q

describe the process of peripheral T cell tolerance?

A
  • not all self reactive T cells are eliminated centrally
  • T cell activation is a 3 signal process
  • signal 1 but no signal 2 = anergy (absence of normal immune response)
  • Signal 1&2 but not 3 = apoptosis
76
Q

where does central tolerance of B cells occur?

A

bone marrow

77
Q

does central B cell tolerance contain positive selection, negative selection or both positive and negative selection?

A

just negative

78
Q

does central T cell tolerance contain positive selection, negative selection or both positive and negative selection?

A

both negative and positive

79
Q

where does peripheral B cell tolerance occur?

A

secondary lymphoid oragns

80
Q

describe the mechanism od peripheral B cell tolerance?

A
  • self reactive b cells still require help from self reactive T cells
  • most self reactive T cells have been eliminated
  • self reactive B cells do not recieve T cell help ad become anergic
81
Q

breach of tolerance may cause what?

A

autoimmune disease

82
Q

cross talk between B and T cells in lymphoid organs ensures the generation of what?

A

cellular and humour adaptive immunity and memory

83
Q

what is the function tolerance?

A

ensure immune system does not attack self antigens

84
Q

describe the process of thymus education

A
  • pre-thymic cells enter thymus, they express both CD8 and CD4 at low levels
  • as they mature they move into the cortex where positive section takes place
  • those cells incapable of binding MHC are phagocytosed
  • dendritic cells and macrophages express auto antigens during negative selection
  • remaining cells migrate to medulla and enter periphery
85
Q

which immune cells do lymph nodes contain?

A

b cells, t cells and dendritic

86
Q

which cells are responsible for activating CD4+ T cells?

A

dendritic

87
Q

the binding of an antigen to a TCR is not enough to prime a naive T cell, what else is required?

A
  • CD28 must bind CD80/86

- cytokines also needed

88
Q

during T cell priming, what determines whether the T cell will be CD4 or CD8

A

cytokines released by the antigen presenting dendritic cell

89
Q

T helper cells/CD4+ cells can be divided into 5 subsets, what are these?

A
  • Th17 cells
  • Th1 cells
  • Th2 cells
  • Tfh cells
  • T reg cells
90
Q

what is the function of Th1 cells?

A

promote cellular immunity particularly in macrophages

91
Q

what is the function of Th17 cells?

A

express IL-17, support innate immunity

92
Q

what is the function of Th2 cells?

A

support antibody immunity (humoral)

93
Q

what is the function of Tfh cells?

A

support B cell response

94
Q

what is the function of T reg cells?

A

immune suppression, negatively regulate T cell activity

95
Q

what does CD8 activation require?

A

antigen presented on MHC 1 to TCR

96
Q

what is the function of cytotoxic T cells?

A
  • induce apoptosis by releasing contents of granules (granzyme and perforin)
  • perforin facilitates granzyme into cell
  • granzyme induces apoptosis
97
Q

how do dendritic cells prime T helper cells?

A

by presenting antigen of MHC ii