Immunology Flashcards
(190 cards)
1
Q
What is the general purpose of the immune system? (3)
A
Identify and eliminate microorganisms and pathogens
Recognise self and non-self signals
Recognise danger signals from acute inflammation
2
Q
When is the function of the immune system at optimum effectiveness?
A
When it is balanced
3
Q
What are the two consequences of an over-reactive immune system?
A
Autoimmune disease and allergic reaction
4
Q
Define allergic reaction
A
Over-reaction of the immune system to a harmless substance
5
Q
What are the two main consequences of an under-reactive immune system?
A
Susceptibility to cancer and infection
6
Q
State the 5 factors that contribute to the emergence of new infectious diseases
A
Travel Loss of natural habitat Population growth Changes in human behaviour Changes in interaction between pathogen and human
7
Q
How does infection occur?
A
When the the body’s physical barriers to pathogens are breached
8
Q
State the 6 properties of the skin that makes it an effective physical barrier to infection
A
Tightly packed Highly keratinised Multi-layered cells Low pH of 5.5 Low oxygen tension Glands
9
Q
State the 4 substances that the glands of the skin secrete
A
Hydrophobic oils
Ammonia
Antimicrobial peptides
Lysozyme
10
Q
What are lysozymes
A
Enzymes that can break down bacterial cell walls
11
Q
State generally where mucous is found in the body
A
All body cavities that are exposed to the external environment
12
Q
State specifically three areas of the body where mucous is present
A
Respiratory tract
GI tract
Urogenital tract
13
Q
State the 5 ways in which mucous stops pathogen invasion
A
Provides a physical barrier
Contains enzymes that kill pathogens
Contains secretory IgA which stops pathogens from attaching/entering cells
Contains lactorferrin that starves bacteria of iron
Cillia trap and clear pathogens
14
Q
What kind of relationship do we have with commensal bacteria?
A
Symbiotic
15
Q
State the 5 ways in which commensal bacteria provides a barrier to pathogens
A
Production of bactericidins
Reduction of pH in large bowel
Synthesis of Vitamin K and B12
Provide invading bacteria with competition for nutrients
Produce short chain fatty acids that have antimicrobial properties
16
Q
What are commensal bacteria affected by? Give 3 examples
A
Changes in homeostasis, caused by things such age, malnutrition and intercurrent infections
17
Q
How are commensal bacteria eliminated?
A
By broad-spectrum antibiotics
18
Q
What are the three physical barriers (skin, mucous and commensal bacteria) known as and why?
A
Constitutive barrier as they are constantly there, regardless of if they are being used.
19
Q
State the three overriding components of the immune system
A
Specialised cells, tissues and soluble factors.
20
Q
What are the four requirements of the immune system?
A
Identification and response system of self and non-self antigens
Ability to modify its response to different pathogens
Actively promote tissue repair and healing after the pathogen has been eliminated
Immunological memory - remember pathogens
21
Q
State the two components of the immune system
A
The hummoral response and the cell mediated response
22
Q
What is the hummoral response mediated by?
A
Soluble macro-molecules (lipids and proteins) that are found in extracellular secretions
23
Q
What is the cell mediated response mediated by?
A
Leukocytes
24
Q
State the 4 components of the hummoral response
A
Cytokines
Complement system proteins
Acute phase proteins
Antibodies
25
State the three classes of cells involved in the cell mediated response
Phagocytes
Lymphocytes
Mast cells, eosinophils and basophils
26
What are the 3 cells involved in phagocytosis?
Neutrophils
Macrophages and Monocytes
Dendritic Cells
27
State the 3 lymphoctyes
T cells
B cells
Natural killer cells
28
What 4 components of the immune system are utilised in response to a virus?
Cytokines
Antibodies
Cytotoxic T cells
NK cells
29
What is the response to a parasitic worm? (4)
Mast cells
Eosinphils
Basophils
Antibodies
30
What is the response to intracellular bacteria and parasites? (3)
NK cells
CTL
Antibodies
31
What is CTL?
Cytotoxic T cell / Cytotoxic T Lymphocyte
32
What is the response to extracellular bacteria, parasites and fungi? (6)
```
Neutrophils
Macrophages
Complement
Antibodies
CTL
NK cells
```
33
What are the two types of tissues that are involved in the immune system?
Primary lymphoid tissue and secondary lymphoid tissue
34
What happens at primary lymphoid tissue?
Leukocytes are developed
35
What are the two primary lymphoid tissues?
Bone marrow
| Thymus
36
What are leukocytes synthesised from?
A single haemopatic stem cell
37
What is special about the haemopatic stem cell?
It has the ability to differentiate into all types of leukocytes
38
What happens after mitosis for a haemopatic stem cell?
One daughter cell differentiates and the other undergoes mitosis again
39
What does these two fates of a haemopatic stem cell mean?
That it is a constantly self-renewing process
40
What is the secondary lymphoid tissue?
Where the adaptive immune response is activated
41
State the 6 secondary lymphoid tissues
```
Spleen
Lymph nodes
Adenoid
Tonsils
Peyers patch
Large intestine
```
42
What/where is the adenoid?
Lymphatic tissue at the back of the nose/throat
43
What is the consequence of an obstruction in lymphatic ducts?
Lympodema
44
What is the danger to tissue affected by lymphodema?
It is at high risk of infection
45
What are cytokines?
Small proteins or peptides
46
What three things are they produced in response to?
Inflammation
Infection
Tissue damage
47
What is the key role of cytokines in the immune system and why?
Coordination of immune response
| Due to ability to modulate the behaviour of cells
48
How long-lived are cytokines?
Short-lived
49
Where do cytokines act in the body?
Both locally and systemically
50
What cytokine is produced in response to a viral infection?
Interferon
51
What are the two functions of interferon?
Antiviral protein production
| Immunoactive cytokine production
52
What are antibodies composed of?
Protein
53
What are antibodies produced by, and why?
Antigen activated B cells, in response to the presence of an antigen
54
What are antigens?
Any substance that can stimulate an immune reaction
55
What three things do antibodies provide defense against?
Extracellular pathogens, viruses and toxins
56
How do antibodies prevent a viral infection?
They seek out and stick to the virus, meaning it cannot enter the cell
57
Where do T and B cells mature?
Bone marrow
58
Where do T and B cells go once they are mature?
The blood and lymphatic system
59
What is T and B cell's primary role?
Search for non-self antigens
60
Which type of B and T cells are long-lived?
Memory T and B cells
61
What two things happen once a B or a T cell comes into contact with a non-self antigen?
They proliferate very quickly
| Differentiate into their different cell types
62
What are B cells responsible for?
Production and secretion of antibodies
63
What type of pathogen is primarily attacked by T cells?
Intracellular pathogens
64
What are the type types of T cells, and what is their function?
Helper T cells - key regulators of the immune system
| Cytotoxic T cells - kill virally infected cells
65
What is the gold standard for a vaccination?
A vaccination that stimulates both a B and T cell response
66
How does immunological memory occur?
Once the adaptive immune system has recognised and responded to a specific antigen
67
What two cells mediate immunological memory?
B and T cells
68
Describe natural killer cells
Large, granular lymphocytes
69
What are the three types of cells/other that NK cells are able to kill?
Tumour cells
Virally infected cells
Antigen bound pathogens and cells
70
What are the two ways in which NK cells are stimulated?
The presence of viral antibodies on a cell's membrane
| The absence of any antibodies on a cell membrane (ie. no self or viral antigens)
71
Where are mast cells present?
In tissues
72
What kind of tissue do mast cells protect and how?
Mucosal surfaces by attaching to large extracellular parasites
73
What is the function that mast cells play a key role in?
Allergic reaction
74
When the immune system is not being stimulated, where are eosinophils and basophils present, and how many are there?
Small numbers in the blood
75
What happens to the eosinophils and basophils when the body is infected by a parasite? (2)
They multiply rapidly and are recruited to the site of infection by inflammatory signals
76
What are mast cells, eosinophils and basophils responsible for? (3)
The recruitment and release of chemicals like histamine
| Secretion of heparin and cytokines
77
What is the complement system?
A family of proteins
78
Where are complement proteins produced?
In hepatocytes
79
What state are complement proteins in when they are circulating in the body, and what are they known as?
Inactive
| Precursor proteins
80
When complement proteins become activated, what occurs?
A complement cascade.
81
How does a complement cascade occur? (2)
First protein is stimulated to cleave into two parts, one of which is an enzyme.
Enzyme then cleaves second protein into two parts, one of which is an enzyme etc.
82
What is at the bottom of a complement cascade and what 3 things can it do?
Components of the immune system that an attack pathogens, recruit and activate other cells
83
What is the role of the complement system?
Promotion of inflammation and defense against certain bacterial species.
84
State the 3 roles of the phagocytic cells
Ingestion and digestion of bacteria and fungi
Ingestion and clearance of debris from the body (immune complexes or apoptotic cells)
Sources of cytokines
85
What are monocytes?
Precursors of macrophages
86
What are the three life stages of a monocyte?
Circulate in the blood
| Migrate to peripheral tissues where they differentiate into macrophages
87
Describe macrophages (2)
Long-lived, tissue resident, phagocytic cells
88
What the four different names for macrophages and where are these in the body?
Liver - Kupffer cells
Lung - Alveolar macrophages
Kidney - Mesangial cells
Nervous system - microglial cells
89
What are the 6 functions of macrophages?
Limit inflammation/regulation of immune response
Tissue repair/wound healing
Antigen presentation
Clearance of debris from dead/dying cells
Ingest and kill extracellular pathogens
Regulate normal tissue homeostasis
90
How can you identify neutrophils?
Bi or tri lobed nucleus
91
What kind of life-span do neutrophils have and why?
Short, as they run out of nutrients
92
How long is the life-span of a neutrophil?
6 hours
93
Where are neutrophils recruited to? (3)
Inflamed, infected or damaged tissue
94
What kind of cells are dendritic cells?
Phagocytic
95
What are the three key roles of dendritic cells?
Engulf antigens
Engulf cellular debris
Antigen presentation
96
What are the three life phases of dendritic cells?
Immature and in peripheral tissues
Activated when exposed to 'phagocytose' antigens
Migrate to secondary lymphoid tissue
97
What is the key function of dendritic cells?
Bridge between innate and adaptive immune system
98
What is the innate immune system responsible for?
The acute inflammatory response
99
How quickly does the innate immune system act?
Very rapidly - within minutes to hours
100
What kind of response is produced by the innate immune system (depending on what type of pathogen is present)?
The same response regardless of what the pathogen is
101
State the 6 components of the innate immune system
```
Acute inflammation
Macrophages
Mast cells
NK cells
Neutrophils
Complement system
```
102
What effect does the innate immune system have on a pathogen (and what can it not do)?
Able to dampen the effect of the pathogen, but not eliminate the infection
103
What kind of response is the adaptive immune system?
Unique response to each pathogen
104
What is the adaptive immune system mediated by (2)?
T and B cells
105
What is the adaptive immune system able to generate?
Immunological memory
106
Describe how the dendritic cells bridge the innate and the adaptive immune system
Collects the antigens from the innate immune system response and presents them the the T and B cells of the adaptive immune system, therefore stimulating a response.
107
What is required for both arms of the immune system to work together?
Biological communication
108
Define immunodeficiency
Complete failure of the immune system
109
How do chronic infections occur?
The pathogen is able to hide from the immune system, meaning it is not attacked fully.
110
What happens to chronic infections?
They periodically reactivate and replicate.
111
What are the two stages of a normal immune response?
The infection is cleared and the pathogen is remembered by the immune system
112
State the two ways in which a pathogen can be recognised
Via direct contact and indirect contact
113
Describe direct contact
The receptor on the immune cell will bind to and interact with ligands on the pathogen, therefore stimulating an immune response
114
Give three examples of receptors and their ligand
TCR (receptor)- MHC
CD40 - CD40L
TLR4 - LPS
115
Describe indirect contact
Injured cells and activated immune cells produce and secrete cytokines which alert and communicate with the immune system
116
How is the immune system stimulated when there is a viral infection?
Virally infected cells produce interferon alpha and beta, which induces an antiviral state in the local environment and the cytokines act on other immune cells and neighbouring cells, instructing them to down regulate protein synthesis.
117
Give three examples of the cytokines produced by viral infection
TNF-alpha
IFN-gamma
Inter-leukins
118
Give the three stages of innate recognition and response
Recognition, activation and effector
119
Specifically, what is recognised in the recognition stage of the innate response?
PAMPs - Pathogen associated molecular patterns
120
What are PAMPs?
Signature molecules that are expressed by pathogens only, and never by humans
121
How are PAMPs recognised?
Using PRRs
122
What are PRRs?
Pattern Recognition Receptors
123
Where are PRRs found?
Extracellularly and intracellularly
124
What two things are involved in the activation and effector phases of the innate immune response?
Acute inflammation and pathogen killing
125
Give two examples of extracellular PRRs and their associated PAMPs
Toll-Like Receptor 4 (TLR4) - Lipopolysaccharide (LPS)
| Dectin 1 - Beta-glucans
126
What are LPS found on?
Gram +ve bacteria
127
What are Beta-glucans found on?
Fungi
128
Give two examples of intracellular PRRs and their associated PAMPs
NOD2 - Muramyl dipeptide
| TLR7 - ssRNA
129
What pathogen has ssRNA?
Viruses
130
What happens when the physical barriers of the immune system are breached and how?
Tissue resident innate immune system cells are activated through PAMPs and danger signals
131
How does an autoimmune disease occur?
When macrophages fail to clear cellular debris
132
State the 5 stages of phagocytosis/clearance of cellular debris
1. Apoptotic cell sends out 'find-me' signals that activates and attracts macrophages
2. Macrophages recognise 'eat-me' signals on the apoptotic cell surface
3. Macrophages rearrange cytoskeleton and internalise the apoptotic cell
4. Lysosomes fuse with the vesicle with the apoptotic cell, creating a phagolysosome
5. Macrophage secretes anti-inflammatory mediators to prevent tissue damage
133
What happens to the pathogens that the macrophage is unable to kill?
They stay in the phagolysosomes
134
State the 3 pathogens that are able to evade killing by the macrophages
Salmonella
Staph, Aureus
Mycobacteria
135
What happens when a pathogen is able to stay alive in the phagolysosome?
The macrophage becomes superativated
136
What stimulates the superactivation of the macrophage?
Pro-inflammatory cytokines
137
What two things does the superactivation of the macrophage do?
Stimulates the production of Reactive Oxygen Species and Reactive Nitrogen Species (ROS and RNS)
Increased presentation capability of macrophages
138
What are the three systemic reactions to cytokines?
Hypothalamus - stimulated to produce prostaglandins = fever
Liver - Acute phase response
Long bones - increase neutrophil production
139
What is the process of neutrophil production called?
Leukocytosis
140
What are the three processes of pathogen killing?
Anti-microbial peptides
ROS
Phagocytosis
141
What two things occur when the PRRs on Mast Cells are stimulated?
The mast cell degranulates
| Production of new pro-inflammatory mediators
142
What is the Acute Phase Response?
A systemic change in plasma concentrations of specific proteins
143
What is the Acute Phase Response driven by?
Cytokines produced by localised inflammatory responses
144
What organ stimulates the Acute Phase Response?
Liver
145
What are the proteins involved in the acute phase response called?
Acute Phase Proteins
146
What are the 5 biological roles of acute phase proteins?
```
Preventing spread of infection
Diagnostic marker
Wound healing
Coagulation
Preventing systemic inflammation
```
147
What acute phase proteins are involved with preventing the spread of infection and can be used as a diagnostic marker?
CRP
SAP (serum amyloid protein)
Complement protein
148
What acute phase protein is involved in wound healing and coagulation?
Fibrinogen
149
What 4 acute phase proteins are involved in preventing systemic infection?
CRP
Haptoglobin
Manganese superdioxide dismutase
Proteinase inhibitors
150
What does CRP stand for?
C-reactive protein
151
What is the structure of CRP?
Pentraxin - 5 identical subunits
152
Clinically, what is CRP used for and why?
Marker of infection as it has a very short half life - so it is a very dynamic marker
153
What does a larger amount of CRP indicate?
The severity and type of infection
154
What are the two other roles of CRP?
Responsible for the initiation of the complement system
| Enhances phagocytosis
155
Where do pro-inflammatory mediators have an affect?
Local affect on the tissue near the production site
156
What are the 4 key elements of acute inflammation?
Increase in vascular permeability
Vasodilation and increase in blood flow
Endothelial cell activation
Transendothelial migration and chemotaxis of neutrophils
157
What are the pro-inflammatory mediators involved in the increase of vascular permeability? (7 - 3 from one cell, 4 from the other)
Macrophages - Nitric oxide, TNF alpha and IL-1
| Mast cells - Histamine, TNF alpha, Prostaglandins and leukotrienes
158
What two pro-inflammatory mediators are involved in vasodilation and increased blood flow? (2)
TNF alpha (macrophages) and Histamine (mast cells)
159
What is endothelial activation?
The expression of Selectins (receptors) and ICAM1/VCAM1 (ligands)
160
What is the consequence of endothelial activation?
Leukocytes stick to endothelial cells that are around the inflammation site
161
What chemical is involved in chemotaxis and what do they do?
Chemokines - family of cytokines that guide migration in chemotaxis
162
What is rolling?
When neutrophils bind weakly to selectin that is expressed on endothelial cells
163
What happens to rolling when ICAM/VCAM are expressed?
The leukocytes binds tightly to endothelial cells
164
What processes does the neutrophil go through to get through the endothelial cells?
Diapodesis
165
What is diapedesis?
Where the neutrophil changes shape and migrates through the blood vessel walls
166
What are the two key structural features of neutrophils?
Intracellular granules and multi-lobed nucleus
167
How do neutrophils get to the site of inflammation?
Recruited by pro-inflammatory mediators
168
What are the 3 ways in which neutrophils can kill pathogens?
NETs
Degranulation
Phagocytosis
169
How is phagocytosis initiated?
By pathogens secreting chemokine-like signals
170
What are the two methods of phagocytosis?
Anti-microbial proteins
| NADPH oxidase dependant mechanisms
171
Describe phagocytosis via anti-microbial proteins
Proteins contained within granules fuse with the encapsulated pathogen
172
Describe the steps involved in NADPH oxidase dependant mechanism
Neutrophil is acitvated
Assembly of NADPH oxidase complex
Production and release of ROS into the phagolysosome
173
What is the NADPH oxidase dependant mechanism known as?
The respiratory burst
174
What are NETs?
Neutrophil Extracellular Traps
175
How are NETs used to fight infection?
Released by activated neutrophils into the extracellular environment
176
What 3 effects do NETs have on pathogens?
Immobilises pathogen
Prevents the spread of the pathogen
Facilitates its phagocytosis
177
What is degranulation?
The secretion of the anti-microbial proteins into the extracellular environment
178
What is the positive and what is the negative of degranulation?
Positive - direct killing of pathogen
| Negative - can cause tissue damage and systemic inflammation
179
How can complement proteins be activated?
Directly or indirectly by a pathogen
180
What are the three ways in which a complement protein can be broken down?
Mannose-binding lectin pathway
Alternative pathway
Classical pathway
181
Where is mannose found?
On bacterial cell membranes
182
Where is MBL produced and why is it produced?
Liver - as part of the acute phase response
183
What happens when mannose is recognised?
The cleaving of complement proteins is initiated
184
What are the four consequences of the complement cascade?
Pathogen killing
Leukocyte recruitment
Removal of immune complexes
Pathogen opsonisation
185
What is opsonisation?
The coating of pathogens in hummoral factors (opsonins) to facilitate phagocytosis
186
Which complement proteins are involved in leukocyte recruitment?
C3a and C5a
187
What are C3a and C5a known as?
Anaphylatoxins
188
What are the two target sites for C3a and C5a?
Blood vessels and mast cells
189
How does pathogen killing occur with complement proteins?
C3b cleaves C5, which attached to the pathogen surface, initiating membrane attack complexes
190
How is the complement cascade initiated?
By C3 being cleaved into C3a and C3b
