Review Of The Innate Immune System Flashcards
Why do we need a innate immune response?
Adaptive immune response is too slow to protect us from some new pathogens
What is innate immunity?
Involves recognition of broadly conserved features of different classes of pathogens
What are pathogen associated molecular patterns (PAMPS)?
Molecules present only on pathogens and not on host cells
Essential for survival of pathogens
Invariant structures shared by entire class of pathogens
Give some examples of PAMPS
Gram negative bacteria - lipopolysaccharides found in outer membrane
Gram posative bacteria - peptidoglycan found in outer membranes
Bacterial flagellum
Abnormal protein glycosylation
What are pattern recognition receptors PRR?
Host factors that specifically recognise a particular type of PAMP
Germ-line encoded
What are the three different classes of PRR?
Extracellular- recognise PAMPS outside the cell and trigger coward instead response
Intracellular- recognise the PAMPS outside of a cell and trigger coward instead response
Secreted- act to tag circulating pathogens for elimination
What are the 5 components of innate immunity?
The inflammation response
Phagocytosis
Complement
Cytokines and chemokines and anti microbial peptides (AMPs)
Natural killer cells
What is the inflammatory response?
A generic defence mechanism whose purpose is to localise and eliminate injurious agents and to remove damaged tissue components
Triggered by the release of pro inflammatory cytokines and chemokines at the side of infection
Enhanced permeability and extravasation
Enhanced recruitment
Enhanced clotting
Neutrophil recruitment
What cells are phagocytes?
Dendritic cells
Macrophages
Neutrophils
How are pathogens detected by phagocytes?
By detecting phosphatidyserine on exterior membrane surface
By detecting “atypical sugars” on cell surfaces
By scavenger receptors
By detecting complement proteins bound to the pathogen surface
By “passive sampling”
What are the three distinct roles in immunity?
Phagocytosis
Activated macrophages produce Cytokines and chemokines
Peptides from broken down pathogens can be presented through MHC - antigen presenting T cell
what is the compliment?
Heat sensitive component of serum that could augment the ability of antibodies to inactivate antigen
Biochemically complex antibodies dependent effector mechanism leading to:
- opsonisation
- punch holes in target membranes (MAC)
- recruitment of phagocytes cells, vasoactive function
What is the complement system?
Complement protein act as secreted pattern recognition receptors (PRRs) and can be activated by a range of PAMPS
How do phagocytes know when they are infected and when to produce cytokines and chemokines?
PAMPS are recognised by a distinct group of pattern recognition receptors
- TLRs
- NLRs
- RIG like receptors
What are cytokines?
Act to modify the behaviour of cells in the immune response
Most of these are called interleukins
What are chemokines?
Act as chemotactic factors - they create concentration gradients which attract specific cell types to a site of infection
What are interferons (cytokines)?
Secreted factors that are induced by viral infection
Offer cross-protection
Widely distributed in evolution but species specific
What are anti microbial peptides?
Secreted short peptides
Usually work by disrupting cell wall leading to lysis
Some are induced by bacterial infection
Offer broad protection
What are natural killer cells?
4% white blood cells
Lymphocyte like but larger granular cytoplasm
Kill certain tumour and virally infected cells
Target cell destruction is caused by granzymes and performing
How are natural killer cells activated?
By loss of self
MHC molecules on target cell surfaces and up regulation of activating ligands
What is the hostile cell?
Cells have enzymes that can destroy some pathogens
What are some diseases associated with innate immunity?
Complement - Core defects inked to development of autoimmune diseases - lupus
Complement - non core defects linked to development of autoimmune diseases - Neisseris
Lack of interferon responsiveness - sensitivity to viral infections
Macrophage deficiencies - IRF8 mutations linked to susceptibility to TB
