Review of The Innate Immune System Flashcards

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1
Q

What are the features of innate immunity

A
  • Rapid - first line of response
  • No specificity for pathogens
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2
Q

What are PAMP’s

A
  • Molecules present only on pathogens and not on the host
    cells
  • Essential for survival of pathogens
  • Invariant structures shared by entire class of pathogens
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3
Q

Give some examples of PAMPs

A
  • Bacterial flagellin
  • Abnormal protein glycosylation
  • Abnormal nucleic acids - viruses
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4
Q

What are PRRs (Pattern recognition receptors)

A
  • Host factors that specifically recognise a particular
    type of PAMP
  • They are germ-line encoded
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5
Q

What are the different classes of PRRs

A
  • Secreted – they act to tag circulating pathogens for
    elimination (Complement)
  • Extracellular – they recognise PAMPs outside of a cell and
    trigger a co-ordinated response to the pathogen
  • Intracellular (cytoplasmic) – they recognise PAMPs inside a cell and act to co-ordinate a response to the pathogen
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6
Q

What are the core components of innate immunity

A
  • The inflammatory response
  • Phagocytes
  • Complement
  • Cytokines, chemokines and anti-microbial
    peptides (AMPs)
  • Natural Killer cells
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7
Q

What is the purpose of the inflammatory response in innate immunity

A
  • A generic defence mechanism whose purpose is to
    localise and eliminate harmful agents and remove damaged tissue components
  • Triggered by the release of pro-inflammatory
    cytokines and chemokines at the site of infection
  • Enhanced permeability and extravasation
  • Neutrophil recruitment
  • Enhanced cell adhesion
  • Enhance clotting
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8
Q

What is the purpose of Phagocytes in innate immunity?

A
  • Recognise and eat pathogens
  • Produce cytokines and chemokine when infected
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9
Q

How do phagocytes know what to eat

A

Material to be “eaten” is recognised in a number of
ways:

  • By detecting phosphatidylserine on exterior membrane
    surface (cells undergoing apoptosis)
  • By detecting “atypical sugars” (e.g. mannose, fucose, -
    glucan) on cell surfaces
  • By Scavenger receptors
  • By detecting complement proteins bound to the pathogen surface
  • By “passive sampling”
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10
Q

What is the purpose of the complement system in innate immunity?

A
  • The complement system is an evolutionarily ancient
    system, which predates the development of the
    adaptive response
  • The use as an effector mechanism for the latter is
    therefore an adaptation grafted onto the original
    purposes of complement as a vital part of innate
    immunity
  • Complement proteins act as secreted Pattern
    recognition receptors (PRRs) and can be activated by
    a range of PAMPs, and can also be activated by
    “altered self”
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11
Q

How do Phagocytes know when they are infected and when to produce cytokines and chemokines

A
  • PRRs recognise PAMPs and DAMPs which trigger cytokine and chemokine release
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12
Q

What are cytokines and what is their function

A
  • Glycoprotein hormones that affect the immune response
  • Act to modify the behaviour of cells in the immune response
  • Most of these are called interleukins (eg. IL-1
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13
Q

What are chemokines and what is their function

A

Act as chemotactic factors – i.e. they create concentration
gradients which attract (or occasionally repel) specific cell
types to a site of production/infection

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14
Q

What are the function of inteferons

A
  • Secreted factors (type I and type III)
  • Induced by viral infection
  • Offer cross-protection
  • Widely distributed in evolution, from fish upwards,
    but species-specific
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15
Q

What are anti-microbial peptides

A
  • Secreted short peptides (18-45 amino acids)
  • Usually works by disrupting cell wall leading to lysis
  • Some are induced by bacterial infection
  • Offer broad protection
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16
Q

What are natural killer cells

A
  • Lymphocyte-like but larger with
    granular cytoplasm
  • Kill certain tumour & virally
    infected cells
  • Target cell destruction is caused by cytotoxic molecules called
    granzymes & perforins
17
Q

What diseases are associated with defects of the innate immune system

A
  • Complement – core defects (e.g. C3) linked to development of
    autoimmune diseases such as lupus
  • Complement – non-core defects linked to suseptibility to
    specific types of pathogens such as Neisseria
  • Macrophage deficiencies - Chronic granulomatous disease
    (CGD); No oxidative burst for bacterial killing
  • Macrophage deficiencies – IRF8 mutations linked to
    susceptibility to TB
  • Aicardi–Goutières syndrome associated with constitutive
    production of inflammatory cytokines
  • Lack of interferon-responsiveness – sensitivity to viral infection
    (e.g. COVID-19)