Innate Immunity Flashcards

(45 cards)

0
Q

Define infectious disease

A

When the pathogen succeeds in evading and/or overwhelming the host’s immune defences

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1
Q

What is the immune system?

A

Cells and organs that contribute to immune defences against infectious and non-infectious conditions

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2
Q

Four roles of the immune system?

A

Pathogen recognition
Containing/eliminating the infection
Regulating itself
Remembering pathogens

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3
Q

Give features of innate immunity that make it different from adaptive

A

Fast
Recognises group pathogens by shared structures
Lack of memory
No change in intensity

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4
Q

What are the first lines of defence in the innate immune system?

A

Physical barriers eg skin, mucous membranes, bronchial cilia

Physiological barriers eg diarrhoea, vomiting, coughing, sneezing

Chemical barriers eg low pH, antimicrobials molecules

Biological barriers eg normal flora

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5
Q

In the first line of defence, where can antimicrobials molecules be found and give examples

A

Tears and saliva have IgA
Sebum, sweat and urine have lysozyme
Mucus
β-defensins in epithelia

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6
Q

How do normal flora prevent infection?

A

Compete with pathogens for attachment sites and resources
Produce antimicrobial chemicals
Synthesise vitamins K and B

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7
Q

Name some flora that inhabit the skin

A
Staph aureus
Staph epidermis
Streptococcus pyogenes 
Candida albicans
Clostridium perfringens
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8
Q

Name some flora that inhabit the nasopharynx

A

Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus species

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9
Q

How can normal flora be displaced from normal location?

A
Breaching skin integrity
Fecal-oral route
Fecal-perineal-urethral route
Poor dental hygiene/dental work
Can over grow and become pathogenic in immunocompromised
Can be depleted by antibiotics
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10
Q

Give examples of natural flora that can become depleted with antibiotic use

A

Intestine - get severe colitis caused by C. difficile

Vagina - get thrush when lactobacillus is depleted and Candida albicans can grow more

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11
Q

Give the overall mechanisms of second lines of defence in innate immunity

A

Phagocytes
Complement system
Cytokines/chemokines

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12
Q

Give examples of phagocytes and where they are found

A
Macrophages
Monocytes
Neutrophils
Basophils/mast cells
Eosinophils
Natural killer cells
Dendritic cells
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13
Q

Where are macrophages found and what do they do?

A

Present in all organs
Phagocytosis
Present microbial agents to T cells
Produce cytokines/chemokines

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14
Q

Where are monocytes found and what do they do?

A

Present in blood
Recruited to infection site
Differentiate into macrophages

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15
Q

Where are neutrophils found and what do they do?

A

Present in blood
Increased during infection
Recruited by chemokines to the site of infection
Phagocytose pyogenic bacteria eg staph aureus and strep pyogenes

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16
Q

When are basophils/mast cells seen?

A

Early actors in inflammation
Allergic response
Phagocytosis

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17
Q

What do eosinophils do?

A

Defence against multicellular parasites

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18
Q

What do natural killer cells do?

A

Kill all abnormal host cells (virus infected or malignant)

19
Q

What do dendritic cells do?

A

Present microbial antigens to T cells

20
Q

How do phagocytes recognise pathogens?

A

Microbe have pathogen-associated molecular patterns (PAMPs)

Phagocytes recognise these using their pathogen recognition receptors (PRRs)

21
Q

What can PAMPs be made up of?

A

Carbohydrates
Lipids
Proteins
Nucleic acids

22
Q

What do opsonins do?

A

Bind to microbial surfaces

Cause enhanced attachment of phagocytes and clearance of microbes

23
Q

Give some examples of opsonins

A

Complement proteins - C3b, C4b
Antibodies - IgG, IgM
Acute phase proteins - CRP, mannose-binding lectin

24
What type of bacteria are opsonins essential for clearing? Give examples
Encapsulated bacteria | Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae B
25
What are the mechanisms for phagocyte intracellular killing?
Oxygen dependent | Oxygen independent
26
What does the oxygen-dependent pathway involve?
A respiratory burst of hydrogen peroxide, hydroxyl radical, nitric oxide, singlet oxygen, hydrohalite
27
What does oxygen independent pathway involve?
Lysozyme Lactoferrine/transferring Cationic proteins Proteolytic and hydrolytic enzymes
28
How can the complement system be activated?
Alternative pathway - initiated by cell surface microbial constituents on pathogens MBL pathway - initiated when mannose-binding lectin binds to mannose containing residues of proteins found on Salmonella spp and Candida albicans
29
How do the two pathways activate the complement system?
Cleave proteins which activates them
30
What are the proteins involved in the complement system (overall)?
C1-C9
31
What do C3a and C5a do?
Recruit phagocytes
32
What do C3b and C4b do?
Opsonisation
33
What do proteins C5-C9 do?
Kill pathogens - bind to membrane of the microbe to produce attack complex, puts holes in the membrane
34
What do cytokines and chemokines do in innate immunity?
Cytokines - activate phagocytes | Chemokines - chemoattraction
35
What cytokines/chemokines do macrophages release?
TNF-α IL-1 IL-6
36
When cytokines/chemokines are released, what effect to the have in the liver?
Cause release of CRP and MBL -> complement activation
37
When cytokines/chemokines are released, what effect to the have in the bone marrow?
Cause neutrophil mobilisation
38
When cytokines/chemokines are released, what effect to the have in the hypothalamus?
Increased body temperature
39
What inflammatory actions do cytokines have?
Vasodilation Increased vascular permeability Release of adhesion molecules which attract neutrophils
40
What can happen when microbial toxins cause overreaction of TLR4 receptor on neutrophils, endothelium and monocytes?
Get an excessive inflammatory response | Sepsis and multi-organ failure caused by cytokine shower, coagulopathy, vasodilation, capillary leak
41
What can reduce phagocytosis?
Decreased spleen function (asplenic/hyposplenic) Decreased neutrophils from chemo, dugs, leukaemia, lymphoma Decreased neutrophil function - chronic granulomatous disease (no respiratory burst) - Chediak-Higashi syndrome (no phagolysosome formation)
42
What does the PRR TLR5 recognise?
Flagellin on bacterial flagella
43
What does the PRR TLR2 recognise?
Peptidoglycan on Gram positive bacteria Lipoprotein and lipopeptides on Gram negative bacteria Mycobacteria
44
What does the PRR TLR4 recognise?
Lipopolysaccharide (LPS) on Gram negative | Lipoteichoic acids on Gram positive