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Pathology and Immunity > Adaptive Immunity > Flashcards

Adaptive Immunity Flashcards

1
Q

what are the humoral components of the adaptive immune system

A

antibodies

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2
Q

what are the cellular components of the adaptive immune system

A

t cells and b cells

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3
Q

what is the adaptive immune system

A

this is a specific and acquired immunity that occurs following an innate immune response

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4
Q

when does the adaptive immune response begin

A

occurs within 4-10 days

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5
Q

what are the two main components of the adaptive immune system

A

cell mediated responses
antibody responses

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6
Q

what do t cells do for the adaptive immune system

A

t cells drive cell mediated immunity

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7
Q

what do cell mediated responses include

A

activation of macrophages and natural killer cells

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8
Q

what are the b cells role in adaptive immunity

A

driving humoral immunity

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9
Q

how are pathogens remembered

A

signature t cell and/or b cell receptors

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10
Q

what provides immunological memory

A

t/b cell receptors

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11
Q

describe the series of events of an adaptive immune response

A

infection
transport of the antigen to the lymphoid organs
recognition by naive t and b cells
clonal expansion and differentiation to effector cells
removal of infectious agent

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12
Q

what must come before an adaptive immune response

A

an innate immune response

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13
Q

what are the three main receptors in adaptive immunity

A

t cell receptor
b cell receptor
major histocompatibility complex

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14
Q

describe the genes that code for innate immune receptors

A

the ancestral gene that codes for the protein is very similar from individual to individual

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15
Q

describe the genes that code for adaptive immune receptors

A

they are very different from individual to individual

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16
Q

describe how innate receptors come

A

from highly conserved genes

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17
Q

what are the highly conserved receptors of the AIS

A

pattern recognition receptors:
- toll like
- dectin
- NOD like

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18
Q

what are the highly variable receptors of the AIS

A

type 1 and type 2 of the MHC
t and b cell receptors

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19
Q

describe the role of t cells in adaptive immunity

A

give rise to cellular immunity and are evolved to protect against intracellular microbes and to help b cell responses

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20
Q

how do t cells recognise peptides from antigen presenting cells

A

through the t cell receptor

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21
Q

what is the t cell repertoire

A

the diversity in the t cell receptor

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22
Q

where are t cells made

A

bone marrow

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23
Q

where do t cells mature

A

thymus

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24
Q

what are the different subsets of t cells that exist

A

t helper cells
cytotoxic t cells
regulatory t cells

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25
Q

describe t helper cells

A

these cells function to help support other immune cells to fight threats

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26
Q

describe cytotoxic t cells

A

these destroy out own cells which have become infected

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27
Q

what are cytotoxic t cells usually associated with

A

viral infections

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28
Q

what are the t helper cells

A

th1
th2
th17
tfh

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29
Q

what are the CD4+ cells

A

the t helper cells

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30
Q

what are the CD8+ cells

A

the cytotoxic t cells

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31
Q

what are tregs

A

the regulatory t cells

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32
Q

what do all t cells begin as

A

naive t cells before undergoing programming to determine which subset to become

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33
Q

what drives the programming of t cell development

A

dc-t cell interactions

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34
Q

where are type 1 MCH receptors found

A

all immune cells

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35
Q

why is it important that the t cell receptor is diverse

A

because it has to be able to detect and respond to billions of different antigens during a person’s lifecycle

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36
Q

where is MHC1 found

A

all nucleated cells

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37
Q

where are MHC2 cells found

A

macrophages
b cells
dendritic cells

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38
Q

what is CD8

A

co receptor that binds to MHC1

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39
Q

what is CD4

A

co receptor that binds to MHC2

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40
Q

what is CD3

A

co receptor that is involved in activation of both CD4+ and CD8+ t cells

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41
Q

which MHC receptors have CD3

A

both type 1 and type 2

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42
Q

what are 95% of t cells in the circulation structured like

A

with alpha and beta chains

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43
Q

what are a small population of t cells in the circulation made up of

A

gamma and delta chains

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44
Q

what are the two main regions of a receptor

A

constant region
variable region

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45
Q

what are the three gene segments that encode the variable region

A

VDJ

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46
Q

what are the VDJ gene segments

A

variable - alpha and beta chains
diversity - beta chain only
joining - alpha and beta chains

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47
Q

describe the structure of the constant region on receptors

A

similar to that of t cells

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48
Q

what are the VDJ responsible for

A

encoding for proteins found in the variable region.
t cells develop the process by rearrangement of the different components of the segments

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49
Q

what is somatic recombination

A

the rearrangement of genes in the t cell receptor

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50
Q

what drives somatic recombination

A

RAG recombinase enzymes

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51
Q

how many combinations for VDJ

A

hundreds of billions

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52
Q

what does somatic recombination allow for

A

different antigen binding sites

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53
Q

what are the pre thymic t cells

A

undifferentiated lymphocytes

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54
Q

what form are t cells in when they first enter the thymus

A

pre thymic t cells

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55
Q

what do t cells interact with in the thymus

A

thymic cortical epithelial cells

56
Q

what must pre thymic t cells undergo in the thymus in order to be educated

A

positive and negative selection

57
Q

describe positive selection

A

this is when the t cell responds to the self antigen- this can be detected by an excessive response to the MHC receptor. if this happens, the cell is lysed

58
Q

describe negative selection

A

you want the t cells to have a level of moderate binding to the MHC receptor on the thymic epithelial cells, otherwise the t cell will not work when it enters the circulation. if there is no recognition, the cell will undergo apoptosis.

59
Q

what is the purpose of thymic cortical epithelial cells

A

present self antigens to t cells to undergo positive and negative selection

60
Q

what happens once the t cells have been positively and negatively selected in the thymus

A

they will leave the thymus and circulate in the blood/lymphatics

61
Q

where do t cells go when they leave the thymus

A

some reside in lymph nodes, as educated, but naive t cells
other go to circulation

62
Q

why are t cells considered to be naive even when they have left the thymus

A

they have not encountered antigens from invading pathogens yet. they will reside in the lymph nodes to wait for antigen presentation from dendritic cells within the lymph nodes

63
Q

what encodes for the t cell receptor

A

VDJ genes

64
Q

what results in t cell activation

A

antigen presentation by dendritic cells

65
Q

describe the steps to phagocytosis

A

recognition
engulfment
phagosome
phagolysosome
cell digestion
residual bodies
exocytosis

66
Q

what are MHC1 receptors functioning or

A

presentation of endogenous proteins like viral and tumour cells found on all nucleated cells

67
Q

describe the function of MHC2 receptors

A

presentation of exogenous proteins in post phagocytosis

68
Q

what do dendritic cells do

A

take up and process the antgien at the epithelial barrier like in the oral mucosa
they migrate to the lymph nodes and mature en route
they have costimulatory activity and can prime naive t cells

69
Q

what are the costimulaotry molecules found in dendritic cells

A

CD40 and CD80

70
Q

why are dendritic cell receptors important for

A

priming native t cells in the lymph nodes

71
Q

where does t cell priming occur

A

lymph nodes

72
Q

what are the signals needed for t cell priming

A

first
second
third

73
Q

describe the first signal for t cell priming

A

binding of the t cell receptor to the antigen that has been presented by the antigen presenting cell. this leads to activation of the t cell

74
Q

describe the second signal of the t cell priming

A

costimulatory receptors come in , and these receptors bind to receptors that are part of the t cell

75
Q

describe the third signal of the t cell priming

A

production of cytokines by dendritic cells, which instructs the t cell whether to become a t helper cell or a cytotoxic t cell
this tells the t cell what to differentiate into.

76
Q

summarise the t cell priming

A

signal 1 - activation of t cells
signal 2 - survival and clonal expansion of t cells. if there is no signal two the t cell is anergic
signal 3 - differentiation into subsets or effector function through the production of cytokines

77
Q

what does anergy arise from

A

activation but no costimulation

78
Q

what happens if t cells are activated in signal one but not signal two

A

they t cell will be anergic, ie non functioning

79
Q

what are the important t cell subsets to know

A

TH2
t regulatory cells
cytotoxic CD8+ cells

80
Q

describe the TH2 cells

A

type 2 helper t cells with a main role in supporting humoral responses and allergic reactions
source of cytokines such as interleukin-4, 5 and 6. these instruct b cells to produce antibodies

81
Q

describe regulatory t cells

A

main role is to function in immune supression
release inhibitory cytokines which inhibit t cell and dendritc cell activation
work to dampen down any excessive inflammatory responses

82
Q

describe cytotoxic t cells

A

activation of these arises from interactions between MHC1 and TCR
they induce host cells to undergo apoptosis and produce enzymes such as granzyme and perforin

83
Q

describe apoptosis

A

programmed cell death.
driven by the production of enzymes that are produced from cytotoxic t cells and natural killer cells

84
Q

summarise the role of b cells in adaptive immunity

A

communicate with t cells and have a specific receptor for antigens
they produce antibodies

85
Q

what does clonal expansion of b cells lead to

A

generation of two subets, plasma cells and memory b cells

86
Q

what are plasma cells

A

antibody factories

87
Q

what are memory b cells important for

A

mounting a quicker response to subsequent infection

88
Q

can b cells present antigens

A

yes, to t cells to activate them

89
Q

where do b cells mature

A

bone marrow

90
Q

where do b cells go after maturation

A

they circulate in the blood and lymph, and are found in large numbers in lymphoid organs

91
Q

how do b cells recognise antigens

A

through the b cell receptor, which is the actual antibody

92
Q

describe diversity in the b cell receptor

A

it means it has the potential to respond to numerous antigens

93
Q

what happens to b cells when they are activated

A

they turn into plasma cells

94
Q

how do b cells leave the bone marrow

A

as immature b cells

95
Q

where do naive mature b cells arise

A

in the periphery

96
Q

describe the b cell receptors

A

have variable and constant regions, and the b cell antibodies have light and heavy chains

97
Q

what does the heavy chain of the b cell receptor involve

A

rearrangement of the VDJ genes

98
Q

what does the light chain of the b cell receptor do

A

rearrangement of VJ genes

99
Q

describe b cell negative selection

A

great diversity, but needs to ensure there is no reactivity against self antigens
b cells undergo negative selection in bone marrow

100
Q

what happens to self reacting b cells in negative selection

A

they are engulfed and removed by macrophages

101
Q

where in the body do b cells undergo negative selection

A

bone marrow

102
Q

what are the five types of immunoglobins

A

IgG
IgE
IgD
IgM
IgA

103
Q

which type of immunoglobins are the b cell receptors

A

IgM and IgD

104
Q

what are the functions of antibodies

A

neutralisation
opsonisation
intitiation of complement

105
Q

what occurs in opsonisation

A

antibody dependent cellular cytotoxicity
mast cell degranulation

106
Q

describe how secretory IgA is involved in antibody production

A
  • produced at mucosal surfaces
  • found in the saliva
  • binds to flagella on microorganisams to prevent their motility
  • binds to and neutralises the bacterial toxins
  • prevents attachment of bacteria to mucosal surfaces
107
Q

describe natural killer cells

A

recognise and kill abnormal cells and invading microbes
there is antibody dependent cellular cytotoxicity and the cells will release granzyme and perforin

108
Q

what drives mast cell degranulation

A

IgE attached to the allergen

109
Q

what are the two types of b cell activation

A

thymus dependent
thymus independent

110
Q

where does b cell activation occur

A

lymph nodes

111
Q

what does activation of b cells result in

A

rise of plasma cells and class switching from IgM and IgG

112
Q

what are thymus dependent b cell activation processes dependent on

A

t cells

113
Q

summarise thymus dependent b cell activation

A
  • requires costimulatory molecules
  • requires cytokine responses from t helper cells
    leads to differentiation in memory b cells and plasma cells
  • uses t helper two cells
  • differentiation into memory b cells and plasma cells
114
Q

which form of b cell activation produces memory b cells

A

thymus dependent

114
Q

describe thymus independent b cell activation

A

stimulation through microbial antigens, direct interactions with things like lipopolysaccharides in bacteria cell walls, and this leads to differentiation into plasma cells.
there is no generation of memory b cells, and no long term immunity

115
Q

what causes class switching

A

b cell activation

116
Q

describe class switching

A

IgM is weak and will switch to IgG, and this occurs by gene rearrangement, but antigen binding sites remain the same.
antibodies have different levels of affinity and avidity

117
Q

does IgG or IgM give a stronger antibody response

A

IgG

118
Q

what is affinity

A

strength of binding of a single antibody to an antigen

119
Q

what is avidity

A

ability of antibodies to form complexes

120
Q

which immunoglobins have high affinity

A

IgG
IgD
IgE

121
Q

which immunoglobins have high avidity

A

IgA
IgM

122
Q

what is the first aitbody to be produced following b cell activation

A

IgM

123
Q

what is involved in immunological tolerance

A

active response to a particular antigen

124
Q

what are the two main types of immune tolerance

A

central and peripheral

125
Q

where is central immune tolerance

A

primary lymphoid organs; thymus and bone marrow

126
Q

what is peripheral immune tolerance

A

this occurs outwith the thymus and bone marrow

127
Q

what can a failure in immune tolerance mechanisms lead to

A

autoimmune diseases

128
Q

do b cells undergo classical positive selection

A

no

129
Q

describe peripheral tolerance

A

some self reactive t cells survive, and enter circulation. dendritic cell can present self peptides to t cell and this will be recognised, and there will be no second signal.

130
Q

what does lack of signal two lead to

A

anergy

131
Q

what does lack of signal three lead to

A

no cytokine production

132
Q

how do t reg cells block activity

A

by binding antigen

133
Q

what does removal of self reactive t cells mean

A

no activation of b cells

134
Q

what can anergic t cells do

A

activate b cells

135
Q

what can a breach of immune tolerance lead to

A

auto immune diseases

Pathology and Immunity (16 decks)

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