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SK299 > Topic 6 - The Immune System > Flashcards

Topic 6 - The Immune System Flashcards

1
Q

What is a pathogen?

A

Any organism which can invade the body and cause disease, such as pathogenic bacteria, fungi, viruses and prions

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2
Q

What is an extracellular pathogen?

In which body parts do they proliferate?

A
  • One which invades the body but not its cells

* Skin, gut, lungs, bodily fluids

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3
Q

What is an intracellular pathogen?

A

One which invades our cells and exploits their functions in order to proliferate

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4
Q

What is the lymphatic system?

A

The network of tissues and organs which help the body rid itself of toxins, waste and other unwanted material

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5
Q

What are the cells of the innate immune system?

A
  • Granulocytes
  • Monocytes
  • Lymphoid cells
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6
Q

What is haematopoiesis?

A

The process which manufactures blood cells

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7
Q

What is the primary function of the lymphatic system?

A

To transport lymph throughout the body

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8
Q

What is lymph?

A

A fluid which contains infection-fighting white cells

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9
Q

What are antigens?

A

Any substance which causes your body to initiate an immune response and produce antibodies against it

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10
Q

What are the primary lymphoid organs?

A
  • Bone marrow

* Thymus

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11
Q

What are the secondary lymphoid organs?

A
  • Lymph nodes
  • Spleen
  • Tonsils
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12
Q

What are facultative intracellular pathogens?

A

Pathogens which can either proliferate outside or inside the host cells

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13
Q

What are obligate intracellular pathogens?

A

Pathogens which can only proliferate inside the host cells

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14
Q

What disease is an example of an obligate intracellular pathogen?

A

Plasmodium falciparum, aka malaria

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15
Q

What are the two types of intracellular pathogen?

A
  • Facultative

* Obligate

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16
Q

What is meant by the term antigenicity?

A

The ability of an antigen to trigger an immune response, which depends on the ability of the host animal to recognise the substance/cell as an antigen in the first place

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17
Q

What are the immune system’s two lines of defence?

A
  • Innate immune system

* Adaptive immune system

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18
Q

What are some of the characteristics of the innate immune system?

A
  • Found in all multicellular organisms
  • Non-specific
  • Exposure quickly leads to response
  • No immunological memory
  • Components: leukocytes, epithelial and connective tissue
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19
Q

What are some of the characteristics of the adaptive immune system?

A
  • Exclusively found in jawed vertebrates
  • Antigen-specific response
  • Delayed maximal response
  • Exposure leads to immunological memory
  • Components: lymphocytes (B and T)
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20
Q

What are the main components of the adaptive immune system?

A
  • B and T lymphocytes
  • Antigen-presenting cells (APCs)
  • Cytokines (signalling molecules)
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21
Q

What are the components of the innate immune system?

A
  • Antimicrobial substances
  • Phagocytosis
  • Cytotoxicity
  • Inflammation
  • Anatomical barriers
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22
Q

What are some examples of antimicrobial substances?

A
  • Lysozyme
  • Complement
  • Interferons
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23
Q

Where is lysozyme found?

A
  • Tears
  • Saliva
  • Mucus
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24
Q

What is Complement?

Where is it found?

A
  • A sequence of about 20 proteins

* Bodily fluids, including blood

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25
Q

What are the three elements of the cascade reaction which Complement causes?

A
  • Self amplification
  • Feedback control
  • Rapidity
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26
Q

What are the three types of immune stem cells?

A
  • Granulocytes
  • Monocytes
  • Lymphoid cells
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27
Q

What is opsonin?

A

A soluble molecule which binds to pathogens or antigens to promote their uptake by phagocytosis

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27
Q

What is phagocytosis?

A

The process by which some white cells engulf and destroy pathogens, cellular debris and toxins

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28
Q

What are eosinophils?

A

A type of white cell

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30
Q

How do eosinophils work, what antigen are they especially affective against?

A
  • They secrete degradative enzymes and toxic substances on to the target cell
  • Parasites
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30
Q

How do NK cells work?

A

They release proteins in to the space between themselves and the target cell, which perforate the target cell membrane and enable pro-apoptotic substances to enter the target cell

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31
Q

What are the two main types of cytotoxic cells?

A
  • Eosinophils

* NK cells

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32
Q

What antigen are NK cells especially effective against?

A

Intracellular pathogens/cancerous cells

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33
Q

What is apoptosis?

A

Programmed cell death

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34
Q

What is the purpose of inflammation?

A

To isolate, inactivate and remove the causative agent and damaged tissue

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35
Q

What are the hallmarks of inflammation?

A
  • Redness
  • Swelling
  • Heat
  • Pain
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36
Q

Where are leukocytes found (in mammals)?

A

Bone marrow

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37
Q

How does lysozyme work?

A

It is an enzyme which splits the chemical bonds (sugars and peptides) that hold together bacterial cell walls, damaging them and so killing the bacterium

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38
Q

Why do bacteria become resistant to antibiotics?

A

As a result of DNA mutations

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39
Q

What is beta-lactamase?

A

An enzyme produced by antibiotic-resistant bacteria

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40
Q

How do beta-lactamases work?

A

By breaking the structure of the antibiotic

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42
Q

What are the characteristics of granulocytes?

A
  • They have secretory granules in their cytoplasm
  • They make up 50-70% of circulating white cells
  • They are sub-divided in to 3 categories
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43
Q

What are the three sub-categories granulocytes are divided in to?

A
  • Neutrophils
  • Basophils
  • Mast cells
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43
Q

What is a macrophage?

A

A type of cell responsible for detecting, engulfing and destroying pathogens and apoptotic cells

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44
Q

What is a phagocyte?

A

A type of cell capable of engulfing and absorbing bacteria and other small cells and particles

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45
Q

What is a macrophage?

A

A type of cell responsible for detecting, engulfing and destroying pathogens and apoptotic cells which also act as a link between the innate and adaptive immune systems by acting as “antigenpresenting cells” to T cells, and secreting Complement components and cytokines

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46
Q

What do dendritic cells do?

A

Patrol the outer surface of the body to identify possible pathogens

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47
Q

What are the characteristics of lymphocytes?

A
  • They make up 25-35% of circulating white cells
  • They’re involved in the innate immune system through cytotoxicity
  • They can attack cancer cells
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48
Q

What are neutrophils?

A

The most abundant subtype of circulating white cell

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49
Q

What do basophils and mast cells do?

A

Contribute to inflammatory response by producing histamine

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51
Q

What can trigger inflammation?

A
  • Histamine
  • Serotonin
  • Prostaglandins
  • Heparin
  • Bradykinin
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51
Q

What do NK cells target?

A

Cells which have become infected with intracellular pathogens, especially cancer cells

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52
Q

What are examples of anatomical barriers?

A
  • Skin
  • Mucous membranes of respiratory, GU and GI tracts
  • Saliva, tears, nasal secretions
  • Stomach acid
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53
Q

What is an effector cell?

A

A cell of various types which actively responds to a stimulus and effects some change

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54
Q

What is an MHC molecule?

A

A cell which is on the outside of immune cells and whose purpose is to sense foreign antigens

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56
Q

What are major histocompatibility complexes (MHCs)?

A

Cell surface molecules which present antigenic peptides to T cells

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57
Q

What are the main components of the adaptive immune system?

A
  • B and T lymphocytes
  • Antigen-presenting cells
  • Cytokines
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57
Q

What are cytokines?

A

Signalling molecules, how the cells of the immune system communicate

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58
Q

What are antigen-presenting cells (APCs)?

A

An immune cell which detects, engulfs and informs the adaptive immune response about an infection

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59
Q

What are cytokines?

A

Signalling molecules; the chemical signals through which immune system cells comunicate

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60
Q

What are some of the functions of cytokines?

A
  • Activate/inactivate immune reactions
  • Help maturation of lymphocytes
  • Recruit immune cells to sites of infection
61
Q

Where do T cell precursors migrate to?

A

The thymus

62
Q

What type of cell do both T and B cells start out as?

A

Progenitor cells

63
Q

What are granzymes?

A

Enzymes which trigger apoptosis

64
Q

What type of cells can T cells and B cells differentiate in to?

A
  • Effector cells

* Memory cells

65
Q

What is an epitope?

A

The part of an antigen molecule which the antibody attaches itself to

66
Q

How is isotype switching achieved?

A

By changing the expression of the non-variable portion of the H chain

67
Q

What is tolerance?

A

The process by which the body recognises self-antigens and healthy tissues

68
Q

What mechanism ensures the elimination of self-reactive T cells?

A

Negative selection

69
Q

What is immunological tolerance?

A

The process by which the body recognises self-antigens and healthy tissues

70
Q

What would be the effect of a defect in negative selection?

A

It could potentially cause autoimmune dise

71
Q

What does idiopathic mean?

A

A disease which arises from internal dysfunctions with no known cause

72
Q

What is HLA?

A

A group of proteins which are resonsible for the regulation of the immune system

73
Q

In people who have the high risk HLA variant, what are the factors which could trigger autoimmune disease?

A

Exposure to certain infections or toxins (including tobacco smoke)

74
Q

Define an allergen

A

Any non-self protein which is tolerant to most people’s immune systems but in certain susceptible individuals, triggers a prologned inflammatory response

75
Q

Which of the divisions of the peripheral nervous system could counteract the dangerous reduction in heart activity caused by anaphylaxis?

A

The sympathetic system as it increases heart rate and blood pressure

76
Q

What is immune system evasion?

A

The mechanisms by which cancer and other pathogens are able to elude the immune system

77
Q

What are granzymes?

A

Serine proteases which induce apoptosis in target cells

78
Q

What are serine proteases?

A

A class of enzyme - one which cleaves peptide bonds in proteins

79
Q

What are the functions of T cells?

A

To directly attack cells infected with viruses

To regulate the immune system

80
Q

Where do T cells mature?

A

The thymus

81
Q

What are CD8+ T cells?

A

Killer, or cytotoxic, T cells

82
Q

Where do T cells migrate to once they are matured?

A
  • Spleen
  • Lymph nodes
  • Bone marrow
  • Blood
83
Q

What are CD4+ T cells?

A

Helper T cells

84
Q

How many classes of antibodies are there?

A

Five

85
Q

What do helper T cells do?

A
  • Assist B cells to produce antibodies

* Assist killer T cells in attacking foreign substances

87
Q

What are the five classes of antibody?

A
  • IgA
  • IgD
  • IgE
  • IgG
  • IgM
87
Q

What is IgA’s main function?

A

To help prevent colonisation by pathogens

88
Q

Where is IgA mainly found?

A
  • B cell membranes

* Mucus membranes

89
Q

Where is IgD mostly found?

A

B cell membranes

90
Q

What is IgD’s main function?

A

Antigen internalisation (helps activate B cells, binds to basophils and mast cells to activate them)

92
Q

What is IgE’s main function?

A
  • Prevents parasitic infections

* Mediates allergic reactions

92
Q

What is special about IgG?

A

It is the only antibody which can cross the placenta

93
Q

What is IgG’s main function?

A
  • Neutralises pathogens such as viruses and bacteria

* Immunological memory

94
Q

Where is IgG mainly found?

A

Blood

96
Q

Where is IgE mainly found?

A
  • B cell membranes

* Biological fluids

97
Q

Where is IgM mainly found?

A
  • B cell membranes

* Blood

98
Q

What is IgM’s main function?

A

Early immune reaction

99
Q

Which types of pathogens are extracellular pathogens?

A
  • Bacteria
  • Fungi
  • Parasites
100
Q

Which types of pathogens are intracellular pathogens?

A
  • Viruses
  • Some bacteria
  • Some parasites
101
Q

What type of stem cells are precursors to immune system cells?

A

Haematopoeitic stem cells

102
Q

What is special about haematopoeitic stem cells?

A

They can differentiate into one of three types of immune system cells

103
Q

What are the immune system cells which haematopoeitic stem cells can differentiate into?

A
  • Granulocytes
  • Monocytes
  • Leukocytes
104
Q

What are the three main components of the immune system?

A
  • Primary lymphoid organs (bone marrow, thymus)
  • Seconary lymphoid organs (lymph nodes, spleen, tonsils)
  • Lymphatic vessels
105
Q

Cancer cells can trigger an immune response. How is this possible given that they are “self” cells?

A

Their expressed proteins are different from the “normal” proteins expressed by the body so therefore not antigenic

106
Q

With regards to the immune system, what do the terms “cell dependent” or “cell independent” mean?

A
  • Cell independent mechanisms do not require any cells of the immune system to be present
  • Cell dependent mechanisms are directly mediated by cells of the immune system
107
Q

Which components of the innate immune system are “cell independent” (not mediated by cells of the immune system)?

A
  • Anatomical barriers

* Antimicrobial substances

108
Q

Which components of the innate immune system are “cell dependent” (are mediated by cells of the immune system)?

A
  • Phagocytes
  • Cytotoxicity
  • Inflammation
109
Q

Why is lysozyme toxic for bacteria but not for human cells?

A

Because human cells do not have bacterial sugar molecules

110
Q

What is a cascade reaction?

A

A reaction which relies on the presence of a series of molecules that exist in an inactive state. They remain inactive until a specific trigger activates the first member of the series, which then activates the second, and so on

111
Q

What is Complement’s effect on a cell?

A

It attacks many sites on the cell surface, punching a large number of tiny holes through the membrane, which can cause cell death

112
Q

How do interferons work?

A

They are a chemical barrier which can interfere with the life cycle of a virus

113
Q

What type of cell is the main kind of phagocyte in the bloodstream?

A

Neutrophils

114
Q

What substances does inflammation trigger the release of?

A
  • Histamine
  • Serotonin
  • Prostaglandins
  • Heparin
  • Bradykinin
115
Q

What is bradykinin?

A

A peptide which promotes inflammation by causing arterioles to dilate and making veins constrict

116
Q

Which naturali antimicrobial substance has a similar mechanism of action to that of antibiotics?

A

Lysozyme - it splits the chemical bonds which hold together the molecular components of bacterial cell walls

117
Q

What are antigen-presenting cells (APCs)?

A

A group of functionally defined cells which are capable of taking antigens and presenting them to lymphocytes in a form they can recognise

118
Q

Which molecules are capable of secreting cytokines?

A
  • Lymphocytes
  • Macrophages
  • Fibroblasts
119
Q

What type of cells are formed when a mature lymphocyte encounters its antigen?

A
  • Memory cells

* Effector cells

120
Q

What can occur if negative selection does not eliminate lymphocytes that react with self-antigens?

A

Autoimmune reactions

121
Q

In order to function properly, T cell receptors also need to be co-activated with what other molecules?

A

CD4 and CD8 molecules

122
Q

What are CD8+ T cells?

A

A class of T lymphocyte that triggers the destruction of cancer cells and self-cells infected by intracellular pathogens

123
Q

What are CD4+ T cells?

A

A class of T lymphocyte involved in the activation of the innate and adaptive immune system through the production of cytokines

124
Q

What are the main stages of lymphocyte maturation and differentiation?

A
  • During early differentiation, B and T cells are exposed to endogenous ligands (molecules derived from host tissues/cells) which bind to their receptors
  • Only cells with functional receptors survive (+ve selection)
  • The selected cells are then exposed to self-antigens in order to establish immunological tolerance (-ve feedback) - only cells that can recognise non-self antigens survive
  • At first encounter with their antigen, mature cells differentiate into either effector or memory cells
125
Q

Where do B cell precursors mature?

A

Entirely in the bone marrow

126
Q

Where do mature B cells migrate to?

A
  • Lymph nodes

* Spleen

127
Q

Helper T cells are characterised by the expression of which co-receptor?

A

CD4

128
Q

Cytotoxic T cells are characterised by the expression of which co-receptor?

A

CD8

129
Q

All T cells are activated by the binding of a T cell receptor with what?

A

The antigen in a complex with the MHC

130
Q

What are B cells’ main functions?

A
  • The production of antibodies
  • The presentation of antigens to helper (CD4+) T cells
  • The development of memory B cells
131
Q

What are the two main differences between a B cell receptor and a T cell receptor?

A

B cell receptors:

  • Do not need an MHC molecule, instead bind directly to their antigen
  • Can be secreted and circulate in the bloodstream/bodily fluids in the form of a soluble immunoglobulin (antibody)
132
Q

What are somatic mutations?

A

Genetic mutations which occur in the soma (any cell not involved with reproduction)

133
Q

What is isotype switching?

A

The molecular mechanism by which B cells change the type of immunoglobulin they express (e.g. from IgM to IgG)

134
Q

How are B cells activated?

A

When their receptor binds to either soluble or membrane bound antigens

135
Q

In the lymphoid organs, B cells are activated by which cells?

A

CD4+ T cells

136
Q

Which type of mutations change the affinity of the B cell receptor for the antigen?

A

Somatic mutations

137
Q

B cells with the highest or lowest affinity for the antigen will survive?

A

The highest

138
Q

What mechanism enables the immune system to recognise healthy tissues and self-antigens

A

Tolerance. All autoimmune diseases are caused by a defect in self-tolerance

139
Q

What mechanism ensures the elimination of self-reactive T cells?

A

Negative selection

140
Q

What would be the effect of a defect in negative selection?

A

It could cause autoimmune disease

141
Q

What substance does IgE trigger the release of?

A

Pro-inflammatory molecules such as histamine

142
Q

Which part of the peripheral nervous system could counteract the dangerous reduction in heart activity caused by anaphylaxis?

A

The sympathetic nervous system as it can increase heart rate and blood pressure

143
Q

What type of lymphocyte and Ig isotype are involved in immunological memory?

A
  • Memory B and T cells
  • IgM
  • IgG
144
Q

What is meant by the term “active immunity”?

A

Resistance to infection with a specific pathogen, acquired as a result of antibody production by the immune system

145
Q

What is meant by the term “passive immunity”?

A

Resistance to infection with a specific pathogen, acquired as a result of receiving the products of someone else’s active immune response (e.g. maternal antibodies passed on through breast milk)

146
Q

Blood group A can receive blood from which other groups?

A
  • O

* A

147
Q

Blood group B can receive blood from which other groups?

A
  • O

* B

148
Q

Blood group AB can receive blood from which other groups?

A
  • O
  • A
  • B
  • AB
149
Q

Blood group O can receive blood from which other groups?

A
  • O
150
Q

Which blood group is the “universal recipient”?

A

AB

151
Q

Which blood group is the “universal donor”?

A

O

152
Q

What is meant by the term “immune evasion”?

A

Mechanisms by which cancer cells and pathogens elude the immune system

SK299 (15 decks)

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