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Foundations of Medicine JMO > Immunology > Flashcards

Immunology Flashcards

1
Q

What is an immune response against self cells called?

A

Autoimmunity

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2
Q

What is an immune response against non-harmful cells called?

A

Hypersensitivity

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3
Q

What is caused by an under-reaction of the immune system?

A

Cancer and infection

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4
Q

What occurs during Car-T cell therapy?

A

A persons own T cells are genetically modified to target specific cancer cells and reinserted in to fight off cancer

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5
Q

What are the 2 types of immunity?

A

Innate immunity - generic and rapid
Acquired immunity - unique and slow

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6
Q

How does the skin act as a physical barrier against pathogens?

A

It is composed of tightly packed, highly-keratinised cells that are sloughed off and constantly renewed

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7
Q

How does the skin act as a physiological barrier against pathogens?

A

It is acidic and has a pH of 5.5

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8
Q

What substances are produced by the sebaceous glands to protect against pathogens?

A

Hydrophobic oils
Lysozymes
Ammonia
Antimicrobial peptides

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9
Q

How does the nose and throat protect against pathogens?

A

They have ciliated epithelium and produce mucus to trap pathogens and move them out of the body or into the stomach

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10
Q

How does a pathogen stimulate an immune response?

A

They express Pathogen Associated Molecular Patterns (PAMPs)

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11
Q

How do innate immune cells detect pathogens?

A

They have Pattern-Recognition Receptors (PRRs) on their cell surface for detection of pathogens

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12
Q

What are the 3 modes of ingestion by macrophages?

A

Pinocytosis
Receptor-mediated endocytosis
Phagocytosis

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13
Q

What occurs during phagocytosis by macrophages?

A

Macrophages’ PRRs bind to the pathogens PAMP
The pathogen is ingested into a phagosome in the cytoplasm
Lysosomes fuse with the phagosome and release hydrophilic enzymes and acid to digest the pathogen

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14
Q

What is expressed after phagocytosis by macrophages?

A

Pathogen derived peptides are expressed on MHC-II molecules on the cell surface membrane

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15
Q

What are released during phagocytosis by macrophages?

A

Pro-inflammatory mediators e.g. TNFα (Tumour necrosis factor)

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16
Q

What is opsonisation?

A

The coating of pathogens by soluble factors (opsonins) to enhance phagocytosis

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17
Q

What are some example of opsonins?

A

C3b
C-reactive protein
IgG/IgM (Immunoglobulin G/M)

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18
Q

What type of immune cells are used to destroy large pathogens such as parasites?

A

Mast cells

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19
Q

In what 2 ways do mast cells react to pathogens?

A

Degranulation - release of pre-formed substances from granules e.g. histamines
Gene expression - Production of new inflammatory substances e.g. leukotrienes and prostaglandins

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20
Q

What are the 5 cardinal signs of inflammation?

A

Rubor - Redness
Calor - Heat of extremities
Tumor - Swelling
Dolor - Pain
Function laesa - Loss of function

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21
Q

What causes redness and heat during inflammation?

A

Localised vasodilation causes increased blood flow and metabolism, resulting in heat production

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22
Q

What causes swelling?

A

The endothelium of post capillary venues becomes more permeable, so immune cells and excess fluid moves in

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23
Q

What molecules are present on the endothelial cells to recruit neutrophils?

A

Platelet-Endothelial Cell Adhesion Molecules (PECAMs)

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24
Q

What name is given to the recruitment and activation of neutrophils?

A

Transendothelial migration

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25
Q

How does vasodilation allow transendothelial migration to occur?

A

Vasodilation results in a decrease in blood flow rate, meaning neutrophils are travelling slow enough to move to the edges of the blood vessels (margination), bind to PECAMs and then move into the endothelium (Diapedesis)

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26
Q

What attracts neutrophils into the Tunica intima?

A

Chemicals released by the bacteria

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27
Q

What is an example of a PECAM?

A

ICAM-1 (Intercellular Adhesion Molecule) A.K.A CD54 (Cluster of Differentiation 54)

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28
Q

What are the 3 methods of pathogen destruction by neutrophils?

A

Phagocytosis
Degranulation
Neutrophil Extracellular Traps

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29
Q

What are the 2 methods of phagocytosis by neutrophils?

A

Phagolysosomal killing
ROS-dependant killing

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30
Q

What occurs during Phagolysosomal killing by neutrophils?

A

The neutrophil engulfs the pathogen into a phagosome
Specific granules, azurophilic granules and lysosomes bind to the phagosome

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31
Q

What occurs during ROS-dependant killing?

A

A Reactive Oxygen Species (NADPH oxidase complex) is assembled in the lysosome walls and is then released into the phagolysosome

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32
Q

What occurs in degranulation of neutrophils?

A

Anti-bacterial proteins are released from the granules of the neutrophils, into the extracellular milieu

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33
Q

What is a Neutrophil Extracellular Trap?

A

At the end of their life, neutrophils will release their chromatin and DNA to form a sticky trap to catch bacteria

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34
Q

What is the acute phase response?

A

A hepatocyte mediated response in which concentrations of specific proteins are changed. It is driven by pro-inflammatory mediators released by the activated macrophages

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35
Q

What is the function of C reactive protein?

A

It primes certain bacteria for destruction and plays a role in determining severity and duration of inflammation

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36
Q

What do virally infected cells produce and release in response to infection?

A

α and ß Interferon

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37
Q

What are the 3 functions of Interferon?

A

They signal neighbouring cells to destroy RNA and reduce protein synthesis to prevent viral replication
They signal neighbouring cells to undergo apoptosis
They activate immune cells such as natural killer cells

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38
Q

What is the function of a MHC-I (Major HistoCompatibility class I) receptor?

A

They survey proteins produced by the cell and present fragments of peptides produced by the cell

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39
Q

How does a virus affect the presentation of MHC-I receptors?

A

They prevent the formation or presentation of MHC-I receptors so that they won’t present non-self proteins

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40
Q

What 2 signals are required for the activation of B cells?

A

Antigens
Helping signals

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41
Q

Where in the lymph nodes does B cell activation occur?

A

In the germinal centre

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42
Q

What is the first type of antibody to be produced by short-lived B plasma cells?

A

IgM antibodies

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43
Q

How can some B cells mutate to improve the immune reaction?

A

They can switch from low to high affinity antibody production
They can switch the class of antibody that they produce, such as from IgM to IgG
They can differentiate into long-lived plasma cells or long-lived memory B cells

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44
Q

What 2 processes occur in the germinal centre reaction?

A

Proliferation (reproduction)
Differentiation

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45
Q

What occurs in a somatic hypermutation response?

A

The mutation of antibodies to allow for a tighter fit to protein antigens

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46
Q

What are the 2 signals required for most activation by non-protein antigens?

A

Non-protein antigen
Pathogen Associated Molecular Pattern (PAMP)

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47
Q

What are repetitive antigenic epitomes?

A

A large number of the same B cell receptor to the same antigen

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48
Q

What is required to activate a B cell containing repetitive antigenic epitomes?

A

Many copies of the antigen without the need for the PAMP

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49
Q

What are the characteristics of a non-protein antigenic response?

A

Only low-affinity antibodies produced
Only short-lived plasma cells produced
No B memory cells

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50
Q

What 2 stimuli are required to activate a B cell, when a protein antigen is present?

A

The protein antigen
T-h cell (CD4+ T cell) stimulation

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51
Q

What types of MHCs do B cells express?

A

Both class I and class II as they can phagocytose a pathogen and splay its antigens

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52
Q

How do T - Follicular Helper cells activate B cells?

A

T-fh cells have a receptor complementary to the MHC-II and protein antigen complex
This causes the T-fh cell to release co-stimulatory molecules that re-activate B cells

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53
Q

What happens to a B cell after it has been activated by a T-fh cell?

A

It proliferates and more T-fh activate the further copies of the B cells
They then differentiate to form long-lived B plasma cells

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54
Q

What is the complement system?

A

A system of low level, inactive proteins that circulate in the blood. When activated, they trigger a chain reaction that amplifies to produce a large response to a pathogen

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55
Q

What does the complement system promote?

A

Opsonisation
Direct killing
Acute inflammation
Leukocyte recruitment

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56
Q

What are the 3 pathways of C3 breakdown?

A

Classical pathway
Mannose-binding lectin pathway
Alternative pathway

57
Q

What enzyme converts C3 into C3b and C3a?

A

C3 convertase enzyme

58
Q

What occurs in the Mannose-binding lectin pathway?

A

MBL binds to mannose of the surface of a bacterium
This causes the activation of the MBL which in turn activates the C3 convertase enzyme

59
Q

What occurs in the alternative pathway?

A

C3b binds to the surface of a pathogen
This stabilises the C3b and triggers the activation of C3 convertase enzyme

60
Q

What occurs in the classical pathway?

A

Planar IgM or IgG bind to the surface of a pathogen by their antigens
IgM converts to a staple form and both IgG and IgM act as a platform for C1 to bind
C1 can then activate C3 convertase enzyme

61
Q

What are the functions of C3b in the complement system?

A

C3b can act as an opsonin
C3b can also activate the enzyme C5 convertase enzyme

62
Q

What is the function of the C5 convertase enzyme?

A

It hydrolyses C5 to form C5b ad C5a

63
Q

What is the function of C5b?

A

It attaches to the surface of a pathogen and begins the formation of an MAC (Membrane Attack Complex)

64
Q

What are the components of an MAC?

A

C5b, C6, C7, C8 and C9

65
Q

What is an MAC?

A

A membrane attack complex is a pore that is formed in the membrane of a pathogen that causes cell death by osmotic lysis

66
Q

What is the function of C3a and C5a?

A

They are pro-inflammatory substances so promote acute inflammation

67
Q

What are the 2 types of T cell?

A

CD8+ T cells
CD4+ T cells

68
Q

Where do B cells differentiate?

A

In the bone marrow

69
Q

Where do T cells differentiate?

A

In the Thymus

70
Q

How do T cells get their name?

A

T = Thymus

71
Q

How do B cells get their name?

A

B = Bursa of Fabricius (The place of B cell formation in birds)

72
Q

What forms the antigen receptors on B cells?

A

Antibodies

73
Q

What are the 2 types of polypeptides that make up an antibody?

A

2x Light chains
2x Heavy chains

74
Q

What are the 2 components of a T cell antigen receptor?

A

An α-chain and a ß-chain

75
Q

What do T cell antigen receptors bind to?

A

A complex formed from an antigenic peptide (Not the full protein) and an MHC molecule

76
Q

What is the other name for an MHC (Major Histocompatability Complex)?

A

HLA (Human Leukocyte Antigens)

77
Q

What are the 2 types of MHC molecule?

A

Class-I
Class-II

77
Q

What are the 2 types of MHC molecule?

A

Class-I
Class-II

78
Q

On which cells are MHC-I expressed?

A

An all nucleated cells

79
Q

What T cells bind to MHC-I molecules?

A

CD8+ T cells

80
Q

On which cells are MHC-II expressed?

A

On Antigen Presenting Cells (APCs)

81
Q

What T cells bind to MHC-II molecules?

A

CD4+ T cells

82
Q

What is bound to MHC-I molecules?

A

Self-produced peptides for surveillance

83
Q

What is bound to MHC-II molecules?

A

Antigenic peptides

84
Q

Where do T and B cells circulate?

A

Between the blood, secondary lymphoid tissues and lymphatic vessels

85
Q

What are the 2 zones of the lymph nodes?

A

T zones and B zones

86
Q

How do lymphocytes enter the lymph nodes?

A

Via the afferent lymphatics
Via High Endothelial Venules (HEVs)

87
Q

How do lymphocytes enter the lymph nodes by HEVs?

A

The endothelial cells of the HEVs express adhesion molecules that allow T and B cells to move in

88
Q

How do B cells encounter antigens in the lymph nodes?

A

Opsonised antigens enter the lymph nodes via circulation and are held there until the correct B cell moves into the lymph node, where they bind

89
Q

What stimulus dendritic cells in an immune response?

A

TNFα

90
Q

What change occurs in dendritic cells when stimulated by TNFα?

A

Dendritic cells are stimulated to increase expression of co-stimulatory molecules

91
Q

What occurs when dendritic cells phagocytose antigens and pathogen debris?

A

They express peptide antigens on MHC-II molecules on their cell surface

92
Q

Where do activated dendritic cells move to when activated?

A

They move into the lymph nodes

93
Q

What do dendritic cells do in the lymph nodes?

A

They stimulate and activate T cells in the lymph nodes by MHC-II molecules and co-stimulatory molecules

94
Q

What is agglutination?

A

The action of an antibody when it cross links many antigens to form clumps

95
Q

How does agglutination help in immunity?

A

It increases efficiency of phagocytosis and prevents viruses binding to host cells

96
Q

What are the 5 types of mammalian antibodies?

A

IgM
IgG
IgA
IgD
IgE

97
Q

What are the 2 forms of IgM antibodies?

A

Membrane-bound monomeric
Secreted, pentameric form

98
Q

What is the function of membrane bound, monomeric IgM?

A

It serves as a B cell receptor

99
Q

What is the function of secreted, pentameric IgM?

A

It is the 1st antibody produced in the humeral response.
It is used in agglutination and complement system activation

100
Q

What type of heavy chain does IgM contain?

A

Mu heavy chain

101
Q

What is the most abundant antibody in normal human serum?

A

Monomeric IgG

102
Q

What are the functions of IgG?

A

Agglutination
Complement system activation
Foetal immune protection
Neutralisation
Opsonisation
Natural killer activation

103
Q

How does IgG provide foetal immune protection?

A

IgG receptors on placental cells allow movement of IgG from the maternal circulation to the foetal circulation

104
Q

What is the name given to the low IgG levels after birth, before the baby begins to produce its own antibodies?

A

Hypogammaglobulinemia

105
Q

What occurs during viral uncoating?

A

The virus attaches to the surface of a phagocyte and is endcytosed
It then releases its RNA into the cell so that it can be synthesised by the cell

106
Q

What occurs during neutralisation?

A

Antibodies bind to the capsid of the virus and can either prevent its attachment to the cells surface or can prevent RNA release by fusion interference or capsid stabilisation

107
Q

How do IgG antibodies act as opsonins?

A

Many phagocytes have Igγ receptors on their surface that can bind to IgG antibodies, bound to a pathogen

108
Q

How do antibodies activate natural killer cells?

A

Natural killer cells have antibody-dependent cell-mediated cytotoxicity, in which Igγ receptors on the NK cells can bind to IgG and become activated to cause cell apoptosis and pro-inflammatory cytokines

109
Q

What is the heavy chain present in IgG antibodies?

A

Gamma heavy chain

110
Q

What are the 2 forms of IgD antibodies?

A

Membrane-bound monomeric form
Secreted form

111
Q

What is the function of the membrane-bound monomeric form?

A

They serve as B cell antigens

112
Q

What is the heavy chain present in IgD antibodies?

A

Delta heavy chains

113
Q

What are the 2 forms of IgA antibodies?

A

Monomeric form in serum
Dimeric form in secretory fluids (secretory IgA)

114
Q

What binds IgA in its dimeric form and IgG in its pentameric form?

A

J chains

115
Q

What is the function of IgA in serum?

A

Neutralisation

116
Q

What is the function of secretory IgA?

A

Neonatal defence and neutralisation sat mucosal sites

117
Q

How does secretory IgA provide neonatal defence?

A

sIgA antibodies are transported into the colostrum and breast milk by receptors in breast tissue to protect the GI tract of neonates

118
Q

What type of heavy chain is present in IgA?

A

Alpha heavy chain

119
Q

What type of heavy chain is present in IgE?

A

Epsilon heavy chain

120
Q

What is the function of IgE?

A

They bind to Igε receptors on mast cells and basophils and stimulate degranulation
This can trigger allergic responses such as asthma, allergy and anaphylaxis

121
Q

What molecule stimulates both CD8+ and CD4+ T cells?

A

Dendritic cells as they express both MHC-I and MHC-II

122
Q

What is the inactive form of CD4+ T cells known as?

A

Naïve CD4+ T cells

123
Q

What is the undifferentiated form of CD4+ cells known as?

A

CD4+ Th0 cells

124
Q

What are 4 MAIN types of differentiated CD4+ effector Th cells?

A

Th1 cells
Th2 cells
Tfh cells
Regulatory T cells

125
Q

What is released upon binding of CD4+ T cells that causes activation?

A

Interleukin-2 (IL-2)

126
Q

What is the function of a Th1 cell?

A

They leave the lymph nodes and enter infected tissue
They then bind to infected macrophages and release IFNγ which increases macrophage activity

127
Q

How can some pathogens infect and propagate macrophages?

A

Some pathogens can escape the phagosome and enter the cytosol of the macrophage

128
Q

What are some examples of pathogens that can escape a phagosome?

A

Listeria
Shigella
Mycobacteria
Legionella species

129
Q

How can Th1 cells help in the destruction of pathogens that can escape the phagosome?

A

They switch on the expression of NADPH oxidase genes that produce toxic reactive oxygen species (ROS)

130
Q

What stimulates the differentiation of CD8+ T cells into Cytotoxic T cells?

A

Interleukin-2 (IL-2)

131
Q

How do Cytotoxic T cells destroy cells?

A

CTL bind to MHC-I molecules containing viral peptides on the surface of infected cells
They release substances that cause DNA fragmentation and apoptosis
They then move to the next target

132
Q

What is the function of Perforin released by CTLs?

A

It polymerises to form a pore in the infected cells membrane, inducing cell death by osmotic lysis

133
Q

What is the function of Granzymes released by CTLs?

A

They are a family of serine proteases that activate apoptosis

134
Q

What is the function of granulysin?

A

It induces apoptosis

135
Q

How is an immune response ended?

A

Effector T-cells are short lived and so die
When all pathogens are destroyed, no more cytokines or pro-inflammatory substances are produced
This means macrophages have no pathogenic stimuli, so instead engulf and ingest cell debris from destroyed cells and pathogens
They then release Anti-inflammatory cytokines such as Interleukin-10 (IL-10) and play a part in tissue repair

136
Q

What are examples of acute phase proteins?

A

Mannose-binding lectin
C reactive protein
C3

137
Q

What is the acute phase response?

A

A response to cytokines by the liver in which complement system proteins are released

138
Q

What cells are precursors to dendritic cells and erythrocytes?

A

Myeloid progenitor cells

Foundations of Medicine JMO (56 decks)

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