Innate immunity Flashcards
(28 cards)
basic overview of innate IS
non-specific
rapid
always active
physical + chemical barriers
basic overview of adaptive IS
specific
slower
forms immune memory
cellular and humoral responses
generates Abs
first line of defence
innate immunity mechanisms constitutively produced
- physical, chemical and microbiological
- secreted antimicrobial agents
second line of defence
innate immunity mechanisms mobilised if pathogens breach first line defences
third line of defence
adaptive immune response
- for small minority of infections innate immunity can’t control
constitutive epithelial defences
mechanical/chemical barriers
- skin, mucous production, low pH, osmotic stress etc.
constitutive antimicrobial defences
- enzymes e.g. lysozyme, fatty acids, antimicrobial peptides
bacterial/commensal microbial interactions
- niche competition, AB production by commensals
constitutive humoral defences
blood clotting
- seals wounds, traps microbes + activates other aspects of immunity
complement system
- labels + kills microbes, activates other aspects of immunity
surface epithelia barriers
- mechanical
- chemical
- microbiological
> epithelial cells joined via tight junctions
longitudinal flow of air/ fluid
> fatty acids
antimicrobial peptides
> normal microbiota
skin’s defence mechanisms
- epidermis
constant sloughing of keratinocytes
lysozyme + high salt (acidic) in sweat
commensal microbes competitively exclude pathogens by secreting fatty acids
waxy, water resistant coating
- protects against damage + keeps dry
skin’s defence mechanisms
- dermis
defensins
RNases + DNases
phagocytes e.g. neutrophils + macrophages
peptidoglycan
- structure
- glycan structure
linear glycan strands cross-linked by peptide chains
N-acetylglucosamine
N-acetylmuramic acid
joined by beta 1-4 glycosidic links
lysozyme
- what is it?
- mechanism
antimicrobial enzyme
- in tears, saliva, sweat etc
destroys peptidoglycan -> exposes lipid bilayer -> bacteria lose rigidity of cell wall -> osmotic stress = cell bursts
microbiome composition
- differences
between individuals
between different parts of body
ways into the skin
sweat glands
hair follicles
blood clotting and coagulation
seals breaches in blood vessels + prevents blood loss by forming a fibrin clot
physically traps invading microbes
-> inhibits spread of infection
attracts phagocytic cells
has direct antimicrobial activity e.g. beta-lysine
gut barriers
- mechanical
- chemical
- microbiological
> epithelial cells joined by tight junctions
longitudinal flow of air or fluid
> low pH
antimicrobial enzymes
> normal microbiota
GI tract barriers
low pH in stomach
mucus layer + fluid flow throughout
proteases, lipases + bile released into duodenum
secretion of antimicrobials
competition by commensal microflora
low pH in stomach
- pH
- impacts on cell function
pH 2-5
damage proteins/ impair functions
damage nucleic acids
limit nutrient uptake
kills many pathogens rapidly
mucosal epithelium
extra protective layer to tight junctions in epithelia
- prevents pathogens adhering to cells
mucocilliary escalator + resident microflora protect against pathogens
all mucosal sites have fluid flow + resident microflora
what also happens in the intestine and bladder/urethra?
intestine = peristalsis
bladder + urethra = peristalsis
gut microbiome composition
most extensive
varies along the gut
influence by physiological differences
e.g. higher pH, lower O2 + lower antimicrobials = higher bacterial load
competition by commensal microbes
~500 species of bacteria reaching 10^13 cells in colon
colonise upper mucous layer
competitively exclude + produce antimicrobial agents to inhibit pathogen growth + prevent the establishing
normal outer and inner mucus layers
outer
- habitat for commensals
inner
- impenetrable to bacteria
colitis
inner mucus layer penetrable to bacteria
bacteria contacts with intestinal epithelium
