Review of The Innate Immune System Flashcards
What are the features of innate immunity
- Rapid - first line of response
- No specificity for pathogens
What are PAMP’s
- Molecules present only on pathogens and not on the host
cells - Essential for survival of pathogens
- Invariant structures shared by entire class of pathogens
Give some examples of PAMPs
- Bacterial flagellin
- Abnormal protein glycosylation
- Abnormal nucleic acids - viruses
What are PRRs (Pattern recognition receptors)
- Host factors that specifically recognise a particular
type of PAMP - They are germ-line encoded
What are the different classes of PRRs
- 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
What are the core components of innate immunity
- The inflammatory response
- Phagocytes
- Complement
- Cytokines, chemokines and anti-microbial
peptides (AMPs) - Natural Killer cells
What is the purpose of the inflammatory response in innate immunity
- 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
What is the purpose of Phagocytes in innate immunity?
- Recognise and eat pathogens
- Produce cytokines and chemokine when infected
How do phagocytes know what to eat
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”
What is the purpose of the complement system in innate immunity?
- 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”
How do Phagocytes know when they are infected and when to produce cytokines and chemokines
- PRRs recognise PAMPs and DAMPs which trigger cytokine and chemokine release
What are cytokines and what is their function
- 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
What are chemokines and what is their function
Act as chemotactic factors – i.e. they create concentration
gradients which attract (or occasionally repel) specific cell
types to a site of production/infection
What are the function of inteferons
- Secreted factors (type I and type III)
- Induced by viral infection
- Offer cross-protection
- Widely distributed in evolution, from fish upwards,
but species-specific
What are anti-microbial peptides
- 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
