Adaptive Immunity Flashcards
(136 cards)
1
Q
what are the humoral components of the adaptive immune system
A
antibodies
2
Q
what are the cellular components of the adaptive immune system
A
t cells and b cells
3
Q
what is the adaptive immune system
A
this is a specific and acquired immunity that occurs following an innate immune response
4
Q
when does the adaptive immune response begin
A
occurs within 4-10 days
5
Q
what are the two main components of the adaptive immune system
A
cell mediated responses
antibody responses
6
Q
what do t cells do for the adaptive immune system
A
t cells drive cell mediated immunity
7
Q
what do cell mediated responses include
A
activation of macrophages and natural killer cells
8
Q
what are the b cells role in adaptive immunity
A
driving humoral immunity
9
Q
how are pathogens remembered
A
signature t cell and/or b cell receptors
10
Q
what provides immunological memory
A
t/b cell receptors
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
12
Q
what must come before an adaptive immune response
A
an innate immune response
13
Q
what are the three main receptors in adaptive immunity
A
t cell receptor
b cell receptor
major histocompatibility complex
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
15
Q
describe the genes that code for adaptive immune receptors
A
they are very different from individual to individual
16
Q
describe how innate receptors come
A
from highly conserved genes
17
Q
what are the highly conserved receptors of the AIS
A
pattern recognition receptors:
- toll like
- dectin
- NOD like
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
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
20
Q
how do t cells recognise peptides from antigen presenting cells
A
through the t cell receptor
21
Q
what is the t cell repertoire
A
the diversity in the t cell receptor
22
Q
where are t cells made
A
bone marrow
23
Q
where do t cells mature
A
thymus
24
Q
what are the different subsets of t cells that exist
A
t helper cells
cytotoxic t cells
regulatory t cells
25
describe t helper cells
these cells function to help support other immune cells to fight threats
26
describe cytotoxic t cells
these destroy out own cells which have become infected
27
what are cytotoxic t cells usually associated with
viral infections
28
what are the t helper cells
th1
th2
th17
tfh
29
what are the CD4+ cells
the t helper cells
30
what are the CD8+ cells
the cytotoxic t cells
31
what are tregs
the regulatory t cells
32
what do all t cells begin as
naive t cells before undergoing programming to determine which subset to become
33
what drives the programming of t cell development
dc-t cell interactions
34
where are type 1 MCH receptors found
all immune cells
35
why is it important that the t cell receptor is diverse
because it has to be able to detect and respond to billions of different antigens during a person's lifecycle
36
where is MHC1 found
all nucleated cells
37
where are MHC2 cells found
macrophages
b cells
dendritic cells
38
what is CD8
co receptor that binds to MHC1
39
what is CD4
co receptor that binds to MHC2
40
what is CD3
co receptor that is involved in activation of both CD4+ and CD8+ t cells
41
which MHC receptors have CD3
both type 1 and type 2
42
what are 95% of t cells in the circulation structured like
with alpha and beta chains
43
what are a small population of t cells in the circulation made up of
gamma and delta chains
44
what are the two main regions of a receptor
constant region
variable region
45
what are the three gene segments that encode the variable region
VDJ
46
what are the VDJ gene segments
variable - alpha and beta chains
diversity - beta chain only
joining - alpha and beta chains
47
describe the structure of the constant region on receptors
similar to that of t cells
48
what are the VDJ responsible for
encoding for proteins found in the variable region.
t cells develop the process by rearrangement of the different components of the segments
49
what is somatic recombination
the rearrangement of genes in the t cell receptor
50
what drives somatic recombination
RAG recombinase enzymes
51
how many combinations for VDJ
hundreds of billions
52
what does somatic recombination allow for
different antigen binding sites
53
what are the pre thymic t cells
undifferentiated lymphocytes
54
what form are t cells in when they first enter the thymus
pre thymic t cells
55
what do t cells interact with in the thymus
thymic cortical epithelial cells
56
what must pre thymic t cells undergo in the thymus in order to be educated
positive and negative selection
57
describe positive selection
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
describe negative selection
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
what is the purpose of thymic cortical epithelial cells
present self antigens to t cells to undergo positive and negative selection
60
what happens once the t cells have been positively and negatively selected in the thymus
they will leave the thymus and circulate in the blood/lymphatics
61
where do t cells go when they leave the thymus
some reside in lymph nodes, as educated, but naive t cells
other go to circulation
62
why are t cells considered to be naive even when they have left the thymus
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
what encodes for the t cell receptor
VDJ genes
64
what results in t cell activation
antigen presentation by dendritic cells
65
describe the steps to phagocytosis
recognition
engulfment
phagosome
phagolysosome
cell digestion
residual bodies
exocytosis
66
what are MHC1 receptors functioning or
presentation of endogenous proteins like viral and tumour cells found on all nucleated cells
67
describe the function of MHC2 receptors
presentation of exogenous proteins in post phagocytosis
68
what do dendritic cells do
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
what are the costimulaotry molecules found in dendritic cells
CD40 and CD80
70
why are dendritic cell receptors important for
priming native t cells in the lymph nodes
71
where does t cell priming occur
lymph nodes
72
what are the signals needed for t cell priming
first
second
third
73
describe the first signal for t cell priming
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
describe the second signal of the t cell priming
costimulatory receptors come in , and these receptors bind to receptors that are part of the t cell
75
describe the third signal of the t cell priming
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
summarise the t cell priming
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
what does anergy arise from
activation but no costimulation
78
what happens if t cells are activated in signal one but not signal two
they t cell will be anergic, ie non functioning
79
what are the important t cell subsets to know
TH2
t regulatory cells
cytotoxic CD8+ cells
80
describe the TH2 cells
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
describe regulatory t cells
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
describe cytotoxic t cells
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
describe apoptosis
programmed cell death.
driven by the production of enzymes that are produced from cytotoxic t cells and natural killer cells
84
summarise the role of b cells in adaptive immunity
communicate with t cells and have a specific receptor for antigens
they produce antibodies
85
what does clonal expansion of b cells lead to
generation of two subets, plasma cells and memory b cells
86
what are plasma cells
antibody factories
87
what are memory b cells important for
mounting a quicker response to subsequent infection
88
can b cells present antigens
yes, to t cells to activate them
89
where do b cells mature
bone marrow
90
where do b cells go after maturation
they circulate in the blood and lymph, and are found in large numbers in lymphoid organs
91
how do b cells recognise antigens
through the b cell receptor, which is the actual antibody
92
describe diversity in the b cell receptor
it means it has the potential to respond to numerous antigens
93
what happens to b cells when they are activated
they turn into plasma cells
94
how do b cells leave the bone marrow
as immature b cells
95
where do naive mature b cells arise
in the periphery
96
describe the b cell receptors
have variable and constant regions, and the b cell antibodies have light and heavy chains
97
what does the heavy chain of the b cell receptor involve
rearrangement of the VDJ genes
98
what does the light chain of the b cell receptor do
rearrangement of VJ genes
99
describe b cell negative selection
great diversity, but needs to ensure there is no reactivity against self antigens
b cells undergo negative selection in bone marrow
100
what happens to self reacting b cells in negative selection
they are engulfed and removed by macrophages
101
where in the body do b cells undergo negative selection
bone marrow
102
what are the five types of immunoglobins
IgG
IgE
IgD
IgM
IgA
103
which type of immunoglobins are the b cell receptors
IgM and IgD
104
what are the functions of antibodies
neutralisation
opsonisation
intitiation of complement
105
what occurs in opsonisation
antibody dependent cellular cytotoxicity
mast cell degranulation
106
describe how secretory IgA is involved in antibody production
- 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
describe natural killer cells
recognise and kill abnormal cells and invading microbes
there is antibody dependent cellular cytotoxicity and the cells will release granzyme and perforin
108
what drives mast cell degranulation
IgE attached to the allergen
109
what are the two types of b cell activation
thymus dependent
thymus independent
110
where does b cell activation occur
lymph nodes
111
what does activation of b cells result in
rise of plasma cells and class switching from IgM and IgG
112
what are thymus dependent b cell activation processes dependent on
t cells
113
summarise thymus dependent b cell activation
- 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
which form of b cell activation produces memory b cells
thymus dependent
114
describe thymus independent b cell activation
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
what causes class switching
b cell activation
116
describe class switching
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
does IgG or IgM give a stronger antibody response
IgG
118
what is affinity
strength of binding of a single antibody to an antigen
119
what is avidity
ability of antibodies to form complexes
120
which immunoglobins have high affinity
IgG
IgD
IgE
121
which immunoglobins have high avidity
IgA
IgM
122
what is the first aitbody to be produced following b cell activation
IgM
123
what is involved in immunological tolerance
active response to a particular antigen
124
what are the two main types of immune tolerance
central and peripheral
125
where is central immune tolerance
primary lymphoid organs; thymus and bone marrow
126
what is peripheral immune tolerance
this occurs outwith the thymus and bone marrow
127
what can a failure in immune tolerance mechanisms lead to
autoimmune diseases
128
do b cells undergo classical positive selection
no
129
describe peripheral tolerance
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
what does lack of signal two lead to
anergy
131
what does lack of signal three lead to
no cytokine production
132
how do t reg cells block activity
by binding antigen
133
what does removal of self reactive t cells mean
no activation of b cells
134
what can anergic t cells do
activate b cells
135
what can a breach of immune tolerance lead to
auto immune diseases
