Innate Immune System Flashcards
Immune system definition
a network of specialised cells, tissues and soluble factors that cooperate to kill and eliminate invading pathogens and cancer cells
autoimmunity definition
the immune system attacking the cells of the body when it shouldn’t as they are healthy
what happens if the immune system overreacts
what happens if the immune system underreacts
over: autoimmunity, allergy
under: high risk of cancer, can’t fend of pathogens
what are the structural defences of the innate immune system
tough outer surface which is impermeable to microbes
inner surface bathed continuously in secretions (acid and mucous)
commensal organisms
anti-microbial peptides
what are the specialised cells and molecules of the innate immune response?
phagocytic cells
degranulating cells
secreted proteins
which cell types are phagocytic and what is their role
neutrophils
monocytes and macrophages
dendritic cells
NK cells
first responders, orchestrate initiation of response, recognise, ingest and kill bacteria and yeast
which cell types are degranulating
mast cells
eosinophils
basophils
what types of proteins are secreted as part of the innate immune response
chemokines
cytokines
complement (induced)
which cell types are tissue-resident innate immune cells
macrophage
mast cell
macrophage role
phagocytosis
regulation of inflammation
antigen presentation
tissue repair
mast cell role
pro-inflammatory
parasitic killing mechanisms
linked to allergy
what are PAMPs
pathogen-associated molecular patterns
what are PRRs
pattern recognition receptors
how do immune cells recognise pathogens as ‘non-self’
pathogens express PAMPs which are recognised by specific PRRs expressed by immune cells
what are target pathogens engulfed into during phagocytosis
what do they fuse with
phagosomes
lysosomes (to form phagolysosomes)
what do macrophages do in response to degrading a pathogen and its debris being released into the intracellular fluid
expresses pathogen-derived peptides on MHC-II molecules
what is degranulation of mast cells
release of pre-formed pro-inflammatory substances
what do mast cells do in response to danger signals from damaged cells
degranulation
gene expression (production of new pro-inflammatory substances)
what causes acute inflammation
bacteria trigger macrophages to release cytokines and chemokines
vasodilation and vascular permeability increase causing redness, heat and swelling
inflammatory cells migrate into tissue releasing inflammatory mediators that cause pain
role of neutrophils
activation of the alternative complement pathway
phagocytosis
pro-inflammatory
bacterial killing mechanisms
what do all three complement activation pathways eventually lead to
C3 cleavage to C3b and C3a
what is the complement system
a cascade of chemical reactions that promote acute inflammatory reactions
what does the complement system lead to
opsonisation of pathogens
direct pathogen killing (membrane attack complex)
leukocyte recruitment
lysis
what are the killing mechanisms of neutrophils
phagocytosis
degranulation
neutrophil extracellular traps
which chemokine recruits neutrophils to the site of an infection
TNF alpha
