Innate Immune System Flashcards
1
Q
What is the immune system?
A
Cells and organs that contribute to immune defences against infectious and non-infectious conditions
2
Q
What is an infectious disease?
A
When the pathogen succeds in evading and/or overwhelming the host’s immune defences
3
Q
What are the roles of the immune response?
A
Pathogen recognition
Containing/eliminating the infection
Regulating itself
Remembering pathogens
4
Q
What is required for the immune response to recognise pathogens?
A
Cell surface and soluble receptors
5
Q
What is the purpose of pathogen recognition?
A
Distinguish between infectious and noninfectious diseases
6
Q
How does the immune system contain/eliminate infection?
A
Killing and clearance mechanisms
7
Q
Why is it important that the immune system regulates itself?
A
To produce minimum damage to the host, leading to resolution
8
Q
Why does the immune system remember pathogens?
A
Prevents the disease for reoccurring
9
Q
What are the features of the innate immune system?
A
Fast
Lack of specificity
Lack of memory
No change in intensity of response to primary or secondary encounters
10
Q
How fast does the innate immune system act?
A
Within seconds
11
Q
How specific is the innate immune system?
A
At best it can recognise groups of bacteria
12
Q
What does the first line of immune defence consist of?
A
Barriers that limit entry and growth of pathogens at portals of entry
13
Q
What are the barriers in the first line immune defence?
A
Physical barriers
Physiological barriers
Chemical barriers
Normal flora
14
Q
What are the physical barriers in the innate immune system?
A
Skin
Mucous membranes
Bronchial cilia
15
Q
What is the surface area of the skin?
A
1-2m squared
16
Q
What do mucous membranes line?
A
Cavities exposed to air; Mouth Respiratory tract GI tract Urinary tract
17
Q
What is the purpose of bronchial cilia?
A
Waft trapped microbes to the pharynx for swallowing
18
Q
What are the physiological barriers in the innate immune system?
A
Diarrhoea
Vomiting
Coughing
Sneezing
19
Q
When is diarrhoea a physiological barrier?
A
In food poisioning
20
Q
When is vomiting a physiological barrier?
A
Food poisioning
Hepatitis
Meningitis
21
Q
When is coughing a physiological barrier?
A
Pneumonia
22
Q
When is sneezing a physiological barrier?
A
Sinusitis
23
Q
What are the chemical barriers to infection?
A
Low pH
Antimicrobial molecules
24
Q
Where has low pH to resist infection?
A
Skin
Stomach
Vagina
25
What pH is the skin?
5.5
26
What pH is the stomach?
1-3
27
What pH is the vagina?
4.4
28
What causes the low pH of the vagina?
Lactobacillus commensal bacteria
29
What antimicrobials molecules consist the innate immune system?
```
IgA
Lysozyme
Mucus
Beta-defensins
Gastric acid and pepsin
```
30
Where is IgA found?
Tears
Saliva
Mucous membranes
31
Where is lysozyme found?
Sebum
Respiration
Urine
32
Where is mucus found?
Mucous membrane
33
What secretes beta-defensins?
Mucous membrane epithelia
34
What is the normal flora?
Non pathogenic microbes that are found in strategic locations
35
Where are the normal flora found?
```
Nasopharynx
Mouth/throat
Skin
GI tract
Vagina
```
36
Where is normal flora absent?
Internal organs/tissues
37
What are the benefits of the normal flora?
Compete with pathogens for attachment sites and resources
Produce antimicrobial chemicals
Synthesise vitamins
38
What vitamins are synthesised by the normal flora?
K
B12
Other B vitamins
39
What organisms are found in the normal flora of the skin?
```
Staphylococcus aureus
Staphylococcus epidermidis
Streptococcus pyogenes
Candida albicans
Clostridium perfringens
```
40
What organisms are found in the normal flora of the nasopharynx?
Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus species
41
When can problems occur with the normal flora?
When normal flora is displaced from its normal location to a sterile location
42
How can normal flora be displaced from its normal location to a sterile location?
Breaching the skin integrity
Poor dental hygiene/dental work
Fecal-oral route
Fecal-perineal-urethral route
43
How can the skin integrity be breached?
Skin loss (burns)
Surgery
Injection drug uses
IV lines
44
What can poor dental hygiene and dental work lead to?
Bacteraemia
45
Give three examples of poor dental hygiene or dental work that can lead to bacteraemia
Dental extraction
Gingivitis
Brushing/flossing
46
What patients are at particular risk of dental related bacteraemia?
Asplenic/hyposplenic
Damaged or prosthetic heart valves
Previous infective endocarditis
47
When is the fecal-oral route likely?
In foodbourne infection
48
When is the fecal-perineal-urethral route likely?
Urinary tract infections in women
49
When may the normal flora become overgrown and pathogenic?
When the host becomes immunocompromised
| When normal flora is depleted by antibiotics
50
What may cause a patient to be immunocompromised?
Diabetes
AIDS
Malignant disease
Chemotherapy
51
What can happen in the intestines when the normal flora is depleted by antibiotics?
Severe colitis resulting from clostridium difficile
52
What can happen in the vagina when the normal flora is depleted by antibiotics?
Thrush resulting from candida albicans
53
What is the second line of defence of the innate immune system?
Phagocytes and chemicals that cause inflammation to contain and clear the infection
54
What cells are involved in innate immunity?
```
Macrophages
Monocytes
Neutrophils
Basophils / mast cells
Eosinophils
Natural Killer cells
Dendritic cells
```
55
What kind of cells are macrophages, monocytes, and neutrophils?
Macrophages
56
What organs are macrophages present in?
All organs
57
What do macrophages do?
Ingest and destroy microbes in phagocytosis
Ingest microbial antigens to T cells in adaptive immunity
Produce cytokines/chemokines
58
Where are monocytes present?
Blood
59
What % of the blood are monocytes?
5-7%
60
What do monocytes do?
Recruited to infection site and differentiated into macrophages
61
Where are neutrophils present?
In the blood
62
What % of blood leukocytes are neutrophils?
60%
63
What happens to neutrophil numbers during infection?
Increased
64
What recruits neutrophils to the site of infection?
Chemokines
65
What do neutrophils do?
Ingest and destroy pyogenic bacteria
66
Give two examples of pyogenic bacteria
S. aureus
| Strep. pyogenes
67
What is the role of basophils/mast cells?
Early actors of inflammation (vasomodulation)
68
Where are basophils/mast cells important?
In allergic responses
69
When are eosinophils important?
Defence against multi-cellular parasites (worms)
70
What do NK cells do?
Kill all abnormal host cells (virus infected or malignant)
71
What do dendritic cells do?
Present microbial antigens to T cells in acquired immunity
72
How does pathogen recognition occur?
Through interactions between pathogen-associated molecular patterns (PAMPs) on the microbe and pathogen recognition receptors (PRRs) known as toll like receptors
73
What are the PAMPS for gram negative bacteria?
Lipopolysaccharides (LPS)
Lipoproteins and lipopeptides
Porin
74
What is the PRR for lipopolysaccharides?
TLR4
75
What is the PRR for lipoproteins and lipopeptides?
TLR2
76
What is the PRR for porins?
TLR2
77
What are the PAMPs for gram +ve bacteria?
Peptidoglycan
| Lipoteichoic acids
78
What is the PRR for peptidoglycan?
TLR2
79
What is the PRR for lipoteichonic acids?
TLR4
80
What are the PAMPs for all mycobacteria?
Lipoarabinomannan
| Mannose-rich glycans
81
What is the PRR for lipoarabinomannan?
TLR2
82
What is the PRR for mannose-rich glycans?
TLR2
83
What is the PAMP for bacterial flagella?
Flagellin
84
What is the PRR for flagellin?
TLR5
85
What are opsonins?
Coating proteins
86
What do opsonins do?
Bind to microbial surfaces
87
What does the binding of opsonins lead to?
Enhanced attachment of phagocytes and clearance of phagocytes
88
What are the classes of opsonins?
Complement proteins
Antibodies
Acute phase proteins
89
Give 2 complement proteins that can act as opsonins
C3b
| C4b
90
Give two antibodies that can act as opsonins
IgG
| IgM
91
Give two acute phase proteins that can act as opsonins
C-reactive protein (CRP)
| Mannose-binding lectin (MBL)
92
What is opsonisation essential for?
Clearing encapsulated bacteria
93
Give an example of an encapsulated bacteria
Neisseria meningitidis
94
What do opsonins and PRRs work together to do?
Initiate phagocytosis
95
What happens once a microbe has been recognised by receptors on the surface of the phagocyte?
The microbe is engulfed and destroyed
96
What happens in the process of phagocytosis?
1. Chemotaxis and adherence of microbe to phagocyte
2. Ingestion of microbe by phagocyte
3. Formation of a phagosome
4. Fusion of the phagosome with a lysosome to form a phagolysosome
5. Digestion of ingested microbe by enzymes
6. Formation of a residual body containing indigestible material
7. Discharge of waste material
97
How do phagocytes kill pathogens?
Using different intracellular killing mechanisms
98
What intracellular killing mechanisms are used by phagocytes?
Oxygen-dependant pathway (respiratory burst)
| Oxygen independent pathways
99
What happens in the oxygen-dependant pathway of phagocytic killing?
Releases toxic O2 products to kill the pathogens
100
What toxic O2 products are released in the respiratory burst?
```
Hydrogen peroxide
Hydroxyl radical
Nitric oxide
Singlet oxygen
Hypophalite
```
101
What are the oxygen-independent pathways of phagocytic killing?
Lysozyme
Lactoferrin or transferrin
Cationic proteins
Proteolytic and hydrolytic enzymes
102
Give an example of a cationic protein
Cathepsin
103
What does the complement system consist of?
20 serum proteins
104
What are the most important serum proteins in the complement system?
C1-9
105
What does C3a and C5a do?
Recruit phagocytes
106
What does C3b-C4b do?
Opsonise pathogens
107
What does C5-C9 do?
Kill pathogens by membrane attack complex
108
What are the activating pathways of the complement system?
Alternative pathway
| MBL pathway
109
What happens in the alternative pathway of complement activation?
Complement initiated by cell surface microbial constituents
110
What happens in the MBL pathway of complement activation?
Complement initiated when MBL binds to mannose containing residues of proteins found on many microbes
111
Give a microbe that will induce the alternative pathway of complement activation
Endotoxins on E. Coli
112
Give two microbes that will induce the MBL pathway of complement activation
Salmonella spp.
| Candida albicans
113
What to cytokine/chemokines cause?
Chemoattraction
Phagocyte activation
Inflammation
114
Give three chemokines
TNF-alpha
IL-1
IL-6
115
Where do TNF-alpha, IL-1, and IL-6 have effects?
Liver
Bone marrow
Hypothalamus
Also have inflammatory actions
116
What is the effect of chemokines in the liver?
Release CRP
| Release MBL, leading to complement activation
117
What is the effect of chemokines in the bone marrow?
Neutrophil mobilisation
118
What is the inflammatory effect of chemokines?
Vasodilation
Vascular permeability
Adhesion molecules lead to attraction of neutrophils
119
What is the effect of chemokines in the hypothalamus?
Increased body temperature
120
When do clinical problems start with the innate immune system?
When there is decreased phagocytosis
121
When may someone have decreased phagocytosis?
Decrease in spleen function
Decreased neutrophil number
Decreased neutrophil function
122
When may someone have decreased spleen function?
Asplenic/hyposplenic patients
123
When may someone have decreased neutrophil numbers?
Cancer chemotherapy
Certain drugs
Leukaemia and lymphoma
124
Give a drug that could lead to decreased neutrophil numbers
Phenytoin
125
When may someone have decreased neutrophil function?
Chronic granulomatous disease
| Chediak-Higashi syndrome
126
Why does chronic granulomatous disease cause a decrease in neutrophil function?
No respiratory burst
127
Why does Chediak-Higashi syndrome lead to reduced neutrophil function?
No phagolysosome formation
