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Infection & Immunity > Innate Immunity > Flashcards

Innate Immunity Flashcards

1
Q

Functions of the innate immune system

A

Prevention of infection
Recognition and response
Activation of adaptive immune system through APCs

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2
Q

What are the primary barriers of the innate immune system

A

Anatomical (physical) barriers
Chemical defences
Commensal flora

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3
Q

Describe the structure skin

A

Epidermis - rightly packed cells (mostly dead) full of kerati. Sites
Dermis - connective tissue, blood vessels, hair follicles, sebaceous and sweat glands etc.
- macrophages, dendritic and mast cells

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4
Q

Describe the skin as an anatomical barrier

A

Low pH ~5.5
Secretion of antimicrobial peptides and proteins
Fatty acid in sebum

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5
Q

Name some anatomical barriers of the innate immune system

A

Skin

Mucosal epithelium: GI, respiratory and urogenital tracts

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6
Q

Describe the structure of mucosal epithelium

A

Outer layer of epithelial cells
Mucus: prevents microbial adhesion to epithelium by trapping them
- beating cilia to expel microbes

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7
Q

Describe mucosal epithelia as a biochemical weapon and anatomical barrier

A

Antibacterial and antiviral substances in saliva, tears and mucus

  • lysozyme: attack’s cell walls predominantly gram positive
  • defending, cathelicidins, histatins: secreted by phagocytes
  • IgA: opsonisation of bacteria and viruses
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8
Q

What is opsonisation

A

Process whereby opsonins e.g. IgA, make an invading microorganism susceptible to phagocytosis

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9
Q

What is an opsonin

A

A freely circulating serum molecule which can attach to the surface of microbes or damaged cells thus making them susceptible to ingestion by phagocytosis

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10
Q

How does lysozyme effect bacteria

A

Hydrolysis of peptidoglycan layer exposing membrane bilayer accessible to antimicrobial proteins e.g. defensins

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11
Q

Name some chemical defences of the innate immune system

A

Low pH - skin (5.5), stomach (2), vagina (4.5)
Bile - bile acids effective against helibacter
Pulmonary surfactant - 6 lipids and 4 proteins - prevent alveoli from collapsing at exhalation, collectins in surfactant

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12
Q

How does commensal flora act as a primary barrier in the innate immune system

A
  • Compete with pathogens for colonisation space and nutrients
  • Promote maturation of immune cells
  • Aid polysaccharide digestion and absorption of nutrients by gut cells
  • Antimicrobial activist against pathogens e.g. bacterial fatty acids against Candida
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13
Q

What are the two soluble molecules of the innate immune system

A

Antimicrobial peptides

Pattern recognition molecules

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14
Q

Characteristics of antimicrobial peptides

A

Attach bacteria, fungus and viruses
Positively charged peptides and proteins up to 60 amino acids
Disrupt microbial membranes, inhibit synthesis of DNA, RNA or proteins

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15
Q

Describe the recognition process of antimicrobial peptides

A
  • Utilises a fixed pathogen recognition battery encoded in human genome
  • Microorganisms display particular pathogen associated molecular patterns (PAMPs)
  • PAMPs are detected by pattern recognition receptors (PRR) and PR soluble molecules
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16
Q

Name some PR soluble molecules

A

Mannose-binding lectin (MBL)
C1q
C-reactive protein

17
Q

Describe what mannose-binding lectin does

A

Carbohydrate recognition sites recognise mannose, fructose and N-acetylglucosamine residues which are common in bacteria but not humans Ls
- Activation of Lectin complement pathway

18
Q

True or false: MBL monomers form trimeric clusters of carbohydrate-recognition domains that bind to mannose and fructose residues with high affinity

A

True

19
Q

Name some receptors macrophages have

A 
Mannose receptor
Complement
Scavenger
Lipid (CD36)
Dectin-1
20
Q

Describe non-oxidative attack

A

When lysosomes merge with the phagosome to form a phagolysosome and destroy pathogen

21
Q

Describe oxidative attack

A

Employs reactive oxygen and nitrogen species (ROS and RNS)

22
Q

Describe the process of oxidative attack

A
  • binding of PAMPs leading to activation of NADPH oxidase —> respiratory burst, transient increase in oxygen consumption resulting in prod. Of superoxide O- and Hydrogen peroxide
  • Activation of inductive nitric oxide synthase —> reactive nitrogen species (nitric oxide) forming radicals - intracellular messages
23
Q

True or false: ROS are generated continuously in small amounts in normal cell metabolism

A

True

24
Q

What is respiratory burst

A

The generated ROS are the main mechanism for killing phagocytosis extracellular pathogens

25
Q

What are the reactive oxygen species

A

O2- superoxide
OH. Radical
H2O2 peroxide
ClO- hypochlorite anion

26
Q

What are the reactive nitrogen species

A

NO nitric acid
NO2 nitrogen dioxide
ONOO- peroxynitrate

27
Q

What does Rec2 induce

A

In neutrophils, they induce assembly of NADPH oxidase in the phagolysosome membrane leading to generation of Superoxide.
The resultant acidification releases granule proteases

28
Q

What are the 4 classifications of inflammation

A

Location: Local or Systemic
Time: Acute or Chronic

29
Q

What are the signs of acute inflammation

A

Swelling (leaky blood vessels)
Redness (attraction of blood)
Heat (blood in area)
Pain (chemicals)

30
Q

What are the roles of inflammation in the body

A

To recruit effector molecules at site of infection
To induce local blood clotting to trap pathogens
Initiate tissue repair

31
Q

What systems does tissue damage activate in the blood

A
  • Kinin system: enzymatic cascade leading to increase in vascular permeability, vasodilation and pain, SM contraction
  • Clotting: increase vascular permeability & neutrophil chemotaxis
  • Fibrinolytic: complement activation
  • Complement: anaphylaxaroxins bind to receptors on mast cells —> degranulation —> release of histamines and other mediators
32
Q

What are he roles of mast cells and basophils in inflammation

A

Release of histamine: 23 dif. physiological functions

  • dilation of blood vessels
  • vascular permeability
  • chemotaxis of leukocytes
33
Q

What is leukocyte extravasation

A

Movement of leukocytes out of circulation and towards site of damage

Infection & Immunity (17 decks)

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