immunology Flashcards
1
Q
list the two types of immune responses
A
innate and adaptive
2
Q
list 4 features of innate immunity
A
present from birth, works quickly, general response (not specific), no memory response
3
Q
what are two components of the first line of defence
A
mechanical barriers and chemical factors
4
Q
describe some mechanical barriers of the first line of defense
A
epithelial cells have tight junctions, normal microbiota, cilia that line the respiratory tract, peristalsis of the intestines
5
Q
describe some chemical factors of the first line of defense
A
epithelial cells produce peptides called defensins, then there’s production of mucus/sweat/lysozyme/gastric juice
6
Q
when does the second line of defense come into play
A
when the pathogen succeeds in penetrating the first line of defence
7
Q
what two things is the second line of defense composed of
A
cells and antimicrobial chemicals
8
Q
what types of cells are involved in the second line of defense
A
NK, macrophages, dendritic cells, neutrophils, eosinophils, basophils, mass cells
9
Q
T or F: B cells and T cells are involved in the innate immune response
A
FALSE; they are not
10
Q
in the second line of defense, how are pathogens recognized
A
via the host cell’s PRR (pathogen recognition receptor)
11
Q
what does PRR stand for
A
pathogen recognition receptor
12
Q
what does TLR stand for
A
Toll-like receptor
13
Q
what are TLRs
A
transmembrane proteins that are found on a variety of host cells
14
Q
how many TLRs do humans make
A
at least 10
15
Q
what does the PRR of the host cell recognize (in second line of defense)
A
the PAMP on the pathogen
16
Q
what does PAMP stand for
A
pathogen associated molecular pattern
17
Q
what does TLR4 recognize on the pathogen
A
LPS
18
Q
what does TLR5 recognize on the pathogen
A
the protein that makes up the bacterial flagellum
19
Q
what happens once PRR of the host binds to the pathogen PAMP
A
inflammatory response is initiated
20
Q
what 3 extracellular signaling molecules are produced during the inflammatory response
A
prostaglandins, histamine, pro-inflammatory cytokines
21
Q
list 3 pro-inflammatory cytokines
A
TNFa, IFNy, interleukins
22
Q
describe the array of cells that are present during the inflammatory response
A
macrophages are the first to arrive, dendritic cells are there, neutrophils (all of these = phagocytic)
macrophages + dendritic cells are also antigen-presenting = activation of adaptive immune response
23
Q
give an example of antimicrobial chemicals present in the second line of defense
A
compliment system
24
Q
what does the compliment system consist of
A
a group of serum proteins
25
how does the compliment system act
in a cascade fashion: one activated factor activates the next and so on
26
how many pathways can activate complement
3
27
list the 3 pathways that can activate complement
classical, lectin, alternative
28
describe the classical complement pathway
induced by antibody binding to an antigen on the surface of a pathogen
29
describe the lectin complement pathway
induced by a protein in host that recognizes mannose residues on the surface of pathogens
30
describe the alternate complement pathway
a complement factor can bind directly to the surface of pathogens
31
what is the convergent point of the three complement pathways
C3
32
what does the complement pathway result in
coating of microbes and induction of phagocytosis, pore formation on pathogens and lysis of the pathogen, recruitment of inflammatory cells, stimulation of adaptive immune response
33
list 3 features of the adaptive immune response
specific to a pathogen, slower to respond, has a memory response
34
list the two classes of vertebrate adaptive immune responses
antibody response and the T-cell mediated response
35
what cells does the antibody response involve
B cells
36
what cells does the T-cell mediated response involve
T cells
37
how do T and B cells arise
from lymphoid progenitors
38
where are the lymphoid progenitors that produce B and T cells
bone marrow
39
where do B cell precursors form
bone marrow
40
where do T cell precursors form
thymus
41
list where the precursors of B and T cells are formed
bone marrow and thymus
42
how are effector cells produced in the adaptive immune response
B and T cells migrate to secondary lymphoid organs, and if they encounter an antigen then they become effector cells
43
list 2 secondary lymphoid organs
spleen, lymph nodes
44
T or F: B and T cells circulate continuously between blood and the lymph
true
45
how many polypeptide chains do antibodies have
4: 2 heavy and 2 light
46
what do the heavy and light chains have at their N-term
variable region
47
what is found within the variable region of an antibody
3 hypervariable regions
48
what do heavy and light chains have at their C-term
constant region
49
what is the class of an immunoglobulin determined by
the amino acid sequence of the constant region
50
how many immunoglobulin classes are there? list them
5: gamma, alpha, delta, mu, epsilon
51
what are the two light chain isotypes
kappa and lambda
52
function of IgG
can cross the placenta
53
function of IgA
protects mucous membranes
54
function of IgM
expressed as membrane-bound on B cells (monomeric form)
55
function of IgD
present as a B cell receptor on mature naive B cells
56
function of IgE
involved in anaphylactic reactions and protects against helminths (parasitic worms)
57
what two immunoglobulins do B cells have on their surface
IgD and IgM
58
what is the B cell receptor when B cells are in bone marrow
IgM
59
what receptor do B cells have when they exit the bone marrow
they also express IgD along with IgM
60
what is a mature naive B cell
one that isn't in the bone marrow and expresses both IgD and IgM
61
describe the process of antibody secretion
mature naive B cells are circulating and have both IgM and IgD. If a B cell receptor binds to its specific antigen then it proliferates and differentiates into effector cells. These are called plasma cells and they secrete the antibodies
62
list 4 things the antigen epitope can be
sugars, amino acid side chains, hydrocarbons, aromatic groups
63
list 4 ways that antibodies protect us from disease
agglutination, neutralization, epsonization, complement activation
64
what is agglutination
antibodies can cross-link pathogens together = easier to phagocytose
65
describe neutralization
antibodies inhibit the ability of the pathogen to bind to its receptor on a host cell
66
describe opsonization
pathogen is coated with something that makes it easier to recognize by phagocytes
67
describe complement activation (in regards to antibody protection)
antibody-antigen complexes can activate the complement system, which can lead to lysis of the pathogen
68
name the two mechanisms in which antibodies are produced
combinatorial joining of gene segments + junctional diversification
69
when do combinatorial joining of gene segments + junctional diversification occur
when B cells are developing in the bone marrow (this is prior to antigen exposure)
70
what two regions does the light chain of an antibody have
variable and constant
71
describe what segments are located on the DNA for the light chain
V region and J region segments, and there is a C region that makes the constant region
72
describe the process of light chain synthesis
VJ joining, deletion of intervening DNA via splicing = mRNA for the light chain
73
what enzyme mediates the VJ joining of light chain synthesis
recombinase
74
how many V and J segments does the kappa chain possess
35 V and 5 J
75
T or F: a B cell will have a successfully rearranged kappa chain and lambda chain
false; it will only ever have one successfully rearranged light chain, not both
76
what gene segments does the heavy chain DNA possess
V, D, J, and C that codes for the constant region
77
describe the process of heavy chain synthesis
DJ joining, V-DJ joining, splicing = mRNA for heavy chain
78
how many V, D, and J segments does the heavy chain DNA possess
40 V, 23 D, 6 J
79
what is junctional diversification
when V/D/J segments are being joined together, nucleotides at the junction site can be either added or deleted (random process)
80
where is the mRNA for the light and heavy chains translated
ribosomes on the rough ER
81
where in the cell do the light and heavy chains associated to form the Ig
in the lumen of the ER
82
what Ig molecules do mature naive B cells express
IgM and IgD
83
T or F: the Ig molecules expressed by mature naive B cells all have the SAME antigen-binding site
true!
84
when will a B cell secrete IgM and IgD
when the cell binds to it's antigen (with T cell help)
85
how are the secondary Ig's produced (G, E, A)
via class switching
86
how is class of Ig determined
by the constant region of the heavy chain
87
T or F: different classes of Igs produced by the same B cell will have the same constant regions
false; they will have different constant regions
88
T or F: different classes of Igs produced by the same B cell will have the same variable regions
true!
89
describe how class switching works
VDJ will have already happened. The DNA will have VDJ upstream of all the different constant-coding segments. The DNA will fold via the AID enzyme, and part of it will be cut and then rejoined in a new orientation
90
what is the full name for the AID enzyme
activation induced deaminase
91
helper T cells are CD_+
CD4+
92
cytotoxic T cells are CD_+
CD8+
93
what does MHC stand for
major histocompatibility complex
94
what is the MHC
a collection of genes that encode proteins that allow self from non self recognition
95
what is the human MHC
HLA (human leukocyte antigen) complex
96
what genes do class II MHC have
DP, DQ, DR
97
what genes do class I MHC have
B, C, A
98
what type of cells express class I MHC
nucleated
99
what type of cells express class II MHC
antigen-presenting cells
100
list 3 examples of antigen presenting cells
macrophages, dendritic cells, B cells
101
describe the structure of class I MHC
alpha chain (1,2,3) and beta chain (B2). alpha 1 and 2 make up the peptide binding groove
102
describe the structure of class II MHC
alpha chain (1,2) and beta chain (1,2). Alpha 1 and beta 1 make up the peptide binding groove
103
what is the role of MHC molecules
they present antigens to T cells for inspection
104
what T cells do class I MHC molecules present antigens to
cytotoxic T cells
105
what T cells do class II MHC molecules present antigens to
helper T cells
106
what type of antigens are expressed in the class I MHC pathway
endogenous antigens
107
what type of antigens are expressed in the class II MHC pathway
exogenous antigens
108
describe the class I MHC pathway
a protein has errors so it's targeted for destruction by the addition of ubiquitin. Proteolysis occurs in the proteasome, and then the peptides are actively transported into the ER lumen where the class I MHC molecules are. The peptide is loaded onto the MHC alpha chains which then associate with the invariant chain. MHC is transported to the cell surface via the secretory pathway and the peptide is expressed
109
describe the class II MHC pathway
antigens are taken up into the cell and are processed in endosomes so they're denatured. meanwhile class II MHC are made in the ER and an invariant chain will bind to the binding groove to prevent endogenous peptides from binding. MHC moves through the golgi to the endosome where the chopped antigen is. Inv chain is chopped and a clip segment remains. clip segment is removed by chaperone protein (DM) and the exogenous peptide is loaded into the groove. MHC moves to the surface and peptide is expressed
110
how does the T cell recognize the antigen
via it's T cell receptor (TCR)
111
describe the structure of the TCR
two glycoprotein subunits, each of which is encoded by a somatically rearranged gene (similar to Ig genes). Each chain has a variable and a constant region
112
what type of TCR do most T cells express
an alpha-beta TCR
113
which chain of the TCR is responsible for binding to the antigen
the variable chain
114
how is the TCR produced
combinatorial joining of gene segments + junctional diversification
115
which chromosome contains the gene for the TCR alpha chain
chromosome 14
116
the genes for the TCR alpha chain have similar organization of the Ig ____ chain
light
117
describe TCR alpha chain synthesis
VJ rearrangement occurs, then splicing out of the extra stuff
118
which chromosome contains the gene for the TCR beta chain
chromosome 7
119
the genes for the TCR beta chain have similar organization of the Ig ____ chain
heavy
120
describe TCR beta chain synthesis
DJ rearrangement and then V-DJ rearrangement. Junctional diversity can also occur
121
what are CD4 and CD8
co-receptor molecules on T cells
122
what are the roles of CD4 and CD8 on T cells
they help the T cell recognize their appropriate MHC molecule via the invariant region
123
what is thymic selection
a process in which T cells learn to differentiate between self and non self peptides
124
where does thymic selection occur
the thymus
125
describe the process leading up to thymic selection
bone marrow-derived lymphoid progenitor cells enter the thymus. In the cortex, alpha and beta chain TCR DNA rearrangement occurs. There will be lots of different thymocytes all expressing different TCRs, and these will undergo thymic selection
126
what is positive thymic selection
T cell surives
127
what is negative thymic selection
T cell dies (via apoptosis)
128
T or F: epithelial cells express both class I and II MHC molecules
true! this is because they're antigen presenting AND nucleated
129
what happens to a T cell with no TCR expressed
death
130
what happens to a T cell with TCRs with no recognition of self MHC + self peptide
death
131
what happens to a T cell with TCRs with too strong recognition of self MHC + self peptide
negative thymic selection (signaled death)
132
what happens to a T cell with TCRs with appropriate recognition of self MHC + self peptide
positive thymic selection (signaled survival, so we get a pool of naive T cells)
133
what is the result of positive thymic selection
a pool of naive T cells in the thymus, which can then migrate to secondary lymphoid organs waiting to encounter their TCR specific antigen
134
how does a naive T cell become an effector T cell
via encountering their TCR specific antigen in secondary lymphoid organs
135
how are naive T cells activated (what activates them)
dendritic cells activate them
136
describe how dendritic cells activate naive T cells
a dendritic cell phagocytoses the antigen at the site of infection and presents it on it's surface via MHC class II. If the dendritic cell meets a T helper cell that has a TCR specific for that antigen, cytokines are released by both cells which activates the T cell into an effector cell. Cell proliferates = clone of helper T cells, clone releases cytokines, and these can activate Tc and B cells
137
what are the two requirements for B cell activation
antigen binding to the BCR, and presence of activated helper T cells
138
describe B cell activation
dendritic cell phagocytoses the pathogen + migrates to lymph node to present antigen to class II MHC to helper T cell. When TCR of helper T cell binds to the antigen then it is activated.
at the same time, an antigen migrates to the lymph node and binds to a BCR. antigen is internalized. B cell expresses antigen on class II MHC as a cry for help for T helper cells. T helper cells will interact with the B cell. Then helper T cells release cytokines = activates B cells. B cells differentiate into plasma cells and can undergo class switching
139
what two things do cytotoxic T cells need in order to be activated
need to interact with a dendritic cell presenting an antigen in context with a class I MHC molecule, and they need the help of activated helper T cells
140
describe cytotoxic T cell activation
infected dendritic cell binds to a Tc cell via class I MHC. Then a clone of activated Th cells will interact with it = pool of activated Tc cells. Tc can then recognize target cells that are expressing the same antigen + target for destruction
141
what are two methods of Tc cells killing a target cell
1. binding of the FasL ligand on the T cell surface to the Fas receptor on the target cell. This leads to caspase activation + killing of the extrinsic pathway of apoptosis
2. Tc cell will kill the target through the release of toxic products
142
name two toxic products that a Tc cell can produce
perforin and granzymes
143
describe how Tc cells kill targets via release of toxic products
effector Tc cell will bind to an infected target and release perforin via exocytosis. Perforin produces a pore in the PM of the target cell. Granzymes are released and enter the target cell via the pore. granzyme B activates executioner caspases and the target cell dies via apoptosis
144
T or F: a single Tc cell can kill multiple target cells
true
145
describe how a memory response differs from initial infection
quicker (peaks 2-7 days after exposure), greater magnitude, more prolonged, occurs due to the presence of memory B and T cells
