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BIOL 3321 - cell and molecular bio > immunology > Flashcards

immunology Flashcards

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1
Q

list the two types of immune responses

A

innate and adaptive

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2
Q

list 4 features of innate immunity

A

present from birth, works quickly, general response (not specific), no memory response

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3
Q

what are two components of the first line of defence

A

mechanical barriers and chemical factors

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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

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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

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6
Q

when does the second line of defense come into play

A

when the pathogen succeeds in penetrating the first line of defence

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7
Q

what two things is the second line of defense composed of

A

cells and antimicrobial chemicals

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8
Q

what types of cells are involved in the second line of defense

A

NK, macrophages, dendritic cells, neutrophils, eosinophils, basophils, mass cells

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9
Q

T or F: B cells and T cells are involved in the innate immune response

A

FALSE; they are not

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10
Q

in the second line of defense, how are pathogens recognized

A

via the host cell’s PRR (pathogen recognition receptor)

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11
Q

what does PRR stand for

A

pathogen recognition receptor

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12
Q

what does TLR stand for

A

Toll-like receptor

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13
Q

what are TLRs

A

transmembrane proteins that are found on a variety of host cells

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14
Q

how many TLRs do humans make

A

at least 10

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15
Q

what does the PRR of the host cell recognize (in second line of defense)

A

the PAMP on the pathogen

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16
Q

what does PAMP stand for

A

pathogen associated molecular pattern

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17
Q

what does TLR4 recognize on the pathogen

A

LPS

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18
Q

what does TLR5 recognize on the pathogen

A

the protein that makes up the bacterial flagellum

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19
Q

what happens once PRR of the host binds to the pathogen PAMP

A

inflammatory response is initiated

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20
Q

what 3 extracellular signaling molecules are produced during the inflammatory response

A

prostaglandins, histamine, pro-inflammatory cytokines

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21
Q

list 3 pro-inflammatory cytokines

A

TNFa, IFNy, interleukins

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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

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23
Q

give an example of antimicrobial chemicals present in the second line of defense

A

compliment system

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24
Q

what does the compliment system consist of

A

a group of serum proteins

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25
Q

how does the compliment system act

A

in a cascade fashion: one activated factor activates the next and so on

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26
Q

how many pathways can activate complement

A

3

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27
Q

list the 3 pathways that can activate complement

A

classical, lectin, alternative

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28
Q

describe the classical complement pathway

A

induced by antibody binding to an antigen on the surface of a pathogen

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29
Q

describe the lectin complement pathway

A

induced by a protein in host that recognizes mannose residues on the surface of pathogens

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30
Q

describe the alternate complement pathway

A

a complement factor can bind directly to the surface of pathogens

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31
Q

what is the convergent point of the three complement pathways

A

C3

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32
Q

what does the complement pathway result in

A

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

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33
Q

list 3 features of the adaptive immune response

A

specific to a pathogen, slower to respond, has a memory response

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34
Q

list the two classes of vertebrate adaptive immune responses

A

antibody response and the T-cell mediated response

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35
Q

what cells does the antibody response involve

A

B cells

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36
Q

what cells does the T-cell mediated response involve

A

T cells

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37
Q

how do T and B cells arise

A

from lymphoid progenitors

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38
Q

where are the lymphoid progenitors that produce B and T cells

A

bone marrow

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39
Q

where do B cell precursors form

A

bone marrow

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40
Q

where do T cell precursors form

A

thymus

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41
Q

list where the precursors of B and T cells are formed

A

bone marrow and thymus

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42
Q

how are effector cells produced in the adaptive immune response

A

B and T cells migrate to secondary lymphoid organs, and if they encounter an antigen then they become effector cells

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43
Q

list 2 secondary lymphoid organs

A

spleen, lymph nodes

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44
Q

T or F: B and T cells circulate continuously between blood and the lymph

A

true

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45
Q

how many polypeptide chains do antibodies have

A

4: 2 heavy and 2 light

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46
Q

what do the heavy and light chains have at their N-term

A

variable region

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47
Q

what is found within the variable region of an antibody

A

3 hypervariable regions

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48
Q

what do heavy and light chains have at their C-term

A

constant region

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49
Q

what is the class of an immunoglobulin determined by

A

the amino acid sequence of the constant region

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50
Q

how many immunoglobulin classes are there? list them

A

5: gamma, alpha, delta, mu, epsilon

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51
Q

what are the two light chain isotypes

A

kappa and lambda

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52
Q

function of IgG

A

can cross the placenta

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53
Q

function of IgA

A

protects mucous membranes

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54
Q

function of IgM

A

expressed as membrane-bound on B cells (monomeric form)

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55
Q

function of IgD

A

present as a B cell receptor on mature naive B cells

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56
Q

function of IgE

A

involved in anaphylactic reactions and protects against helminths (parasitic worms)

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57
Q

what two immunoglobulins do B cells have on their surface

A

IgD and IgM

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58
Q

what is the B cell receptor when B cells are in bone marrow

A

IgM

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59
Q

what receptor do B cells have when they exit the bone marrow

A

they also express IgD along with IgM

60
Q

what is a mature naive B cell

A

one that isn’t in the bone marrow and expresses both IgD and IgM

61
Q

describe the process of antibody secretion

A

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
Q

list 4 things the antigen epitope can be

A

sugars, amino acid side chains, hydrocarbons, aromatic groups

63
Q

list 4 ways that antibodies protect us from disease

A

agglutination, neutralization, epsonization, complement activation

64
Q

what is agglutination

A

antibodies can cross-link pathogens together = easier to phagocytose

65
Q

describe neutralization

A

antibodies inhibit the ability of the pathogen to bind to its receptor on a host cell

66
Q

describe opsonization

A

pathogen is coated with something that makes it easier to recognize by phagocytes

67
Q

describe complement activation (in regards to antibody protection)

A

antibody-antigen complexes can activate the complement system, which can lead to lysis of the pathogen

68
Q

name the two mechanisms in which antibodies are produced

A

combinatorial joining of gene segments + junctional diversification

69
Q

when do combinatorial joining of gene segments + junctional diversification occur

A

when B cells are developing in the bone marrow (this is prior to antigen exposure)

70
Q

what two regions does the light chain of an antibody have

A

variable and constant

71
Q

describe what segments are located on the DNA for the light chain

A

V region and J region segments, and there is a C region that makes the constant region

72
Q

describe the process of light chain synthesis

A

VJ joining, deletion of intervening DNA via splicing = mRNA for the light chain

73
Q

what enzyme mediates the VJ joining of light chain synthesis

A

recombinase

74
Q

how many V and J segments does the kappa chain possess

A

35 V and 5 J

75
Q

T or F: a B cell will have a successfully rearranged kappa chain and lambda chain

A

false; it will only ever have one successfully rearranged light chain, not both

76
Q

what gene segments does the heavy chain DNA possess

A

V, D, J, and C that codes for the constant region

77
Q

describe the process of heavy chain synthesis

A

DJ joining, V-DJ joining, splicing = mRNA for heavy chain

78
Q

how many V, D, and J segments does the heavy chain DNA possess

A

40 V, 23 D, 6 J

79
Q

what is junctional diversification

A

when V/D/J segments are being joined together, nucleotides at the junction site can be either added or deleted (random process)

80
Q

where is the mRNA for the light and heavy chains translated

A

ribosomes on the rough ER

81
Q

where in the cell do the light and heavy chains associated to form the Ig

A

in the lumen of the ER

82
Q

what Ig molecules do mature naive B cells express

A

IgM and IgD

83
Q

T or F: the Ig molecules expressed by mature naive B cells all have the SAME antigen-binding site

A

true!

84
Q

when will a B cell secrete IgM and IgD

A

when the cell binds to it’s antigen (with T cell help)

85
Q

how are the secondary Ig’s produced (G, E, A)

A

via class switching

86
Q

how is class of Ig determined

A

by the constant region of the heavy chain

87
Q

T or F: different classes of Igs produced by the same B cell will have the same constant regions

A

false; they will have different constant regions

88
Q

T or F: different classes of Igs produced by the same B cell will have the same variable regions

A

true!

89
Q

describe how class switching works

A

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
Q

what is the full name for the AID enzyme

A

activation induced deaminase

91
Q

helper T cells are CD_+

A

CD4+

92
Q

cytotoxic T cells are CD_+

A

CD8+

93
Q

what does MHC stand for

A

major histocompatibility complex

94
Q

what is the MHC

A

a collection of genes that encode proteins that allow self from non self recognition

95
Q

what is the human MHC

A

HLA (human leukocyte antigen) complex

96
Q

what genes do class II MHC have

A

DP, DQ, DR

97
Q

what genes do class I MHC have

A

B, C, A

98
Q

what type of cells express class I MHC

A

nucleated

99
Q

what type of cells express class II MHC

A

antigen-presenting cells

100
Q

list 3 examples of antigen presenting cells

A

macrophages, dendritic cells, B cells

101
Q

describe the structure of class I MHC

A

alpha chain (1,2,3) and beta chain (B2). alpha 1 and 2 make up the peptide binding groove

102
Q

describe the structure of class II MHC

A

alpha chain (1,2) and beta chain (1,2). Alpha 1 and beta 1 make up the peptide binding groove

103
Q

what is the role of MHC molecules

A

they present antigens to T cells for inspection

104
Q

what T cells do class I MHC molecules present antigens to

A

cytotoxic T cells

105
Q

what T cells do class II MHC molecules present antigens to

A

helper T cells

106
Q

what type of antigens are expressed in the class I MHC pathway

A

endogenous antigens

107
Q

what type of antigens are expressed in the class II MHC pathway

A

exogenous antigens

108
Q

describe the class I MHC pathway

A

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
Q

describe the class II MHC pathway

A

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
Q

how does the T cell recognize the antigen

A

via it’s T cell receptor (TCR)

111
Q

describe the structure of the TCR

A

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
Q

what type of TCR do most T cells express

A

an alpha-beta TCR

113
Q

which chain of the TCR is responsible for binding to the antigen

A

the variable chain

114
Q

how is the TCR produced

A

combinatorial joining of gene segments + junctional diversification

115
Q

which chromosome contains the gene for the TCR alpha chain

A

chromosome 14

116
Q

the genes for the TCR alpha chain have similar organization of the Ig ____ chain

A

light

117
Q

describe TCR alpha chain synthesis

A

VJ rearrangement occurs, then splicing out of the extra stuff

118
Q

which chromosome contains the gene for the TCR beta chain

A

chromosome 7

119
Q

the genes for the TCR beta chain have similar organization of the Ig ____ chain

A

heavy

120
Q

describe TCR beta chain synthesis

A

DJ rearrangement and then V-DJ rearrangement. Junctional diversity can also occur

121
Q

what are CD4 and CD8

A

co-receptor molecules on T cells

122
Q

what are the roles of CD4 and CD8 on T cells

A

they help the T cell recognize their appropriate MHC molecule via the invariant region

123
Q

what is thymic selection

A

a process in which T cells learn to differentiate between self and non self peptides

124
Q

where does thymic selection occur

A

the thymus

125
Q

describe the process leading up to thymic selection

A

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
Q

what is positive thymic selection

A

T cell surives

127
Q

what is negative thymic selection

A

T cell dies (via apoptosis)

128
Q

T or F: epithelial cells express both class I and II MHC molecules

A

true! this is because they’re antigen presenting AND nucleated

129
Q

what happens to a T cell with no TCR expressed

A

death

130
Q

what happens to a T cell with TCRs with no recognition of self MHC + self peptide

A

death

131
Q

what happens to a T cell with TCRs with too strong recognition of self MHC + self peptide

A

negative thymic selection (signaled death)

132
Q

what happens to a T cell with TCRs with appropriate recognition of self MHC + self peptide

A

positive thymic selection (signaled survival, so we get a pool of naive T cells)

133
Q

what is the result of positive thymic selection

A

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
Q

how does a naive T cell become an effector T cell

A

via encountering their TCR specific antigen in secondary lymphoid organs

135
Q

how are naive T cells activated (what activates them)

A

dendritic cells activate them

136
Q

describe how dendritic cells activate naive T cells

A

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
Q

what are the two requirements for B cell activation

A

antigen binding to the BCR, and presence of activated helper T cells

138
Q

describe B cell activation

A

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
Q

what two things do cytotoxic T cells need in order to be activated

A

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
Q

describe cytotoxic T cell activation

A

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
Q

what are two methods of Tc cells killing a target cell

A
  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
Q

name two toxic products that a Tc cell can produce

A

perforin and granzymes

143
Q

describe how Tc cells kill targets via release of toxic products

A

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
Q

T or F: a single Tc cell can kill multiple target cells

A

true

145
Q

describe how a memory response differs from initial infection

A

quicker (peaks 2-7 days after exposure), greater magnitude, more prolonged, occurs due to the presence of memory B and T cells

BIOL 3321 - cell and molecular bio (19 decks)

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