Lecture 3- Immune mechanisms: pattern recognition and extracellular cascades Flashcards
4 components of am immune system
recognition, response, effect, integration
difference between innate and adaptive receptors
innate or pattern recognition receptors- recognise/respond to agonists, e.g. toll-like receptors
adaptive- recognise/respond to antigens, e.g. antibodies, Tcell receptors
what might trigger pattern recognition receptors
pathogen-derived molecules, or damage caused by pathogens- not sure exactly which
they can also detect damaged self cells, e.g. heat shock signals
example of lectins in the lungs
surfactants SpA and SpD- bind pathogens in the lungs to help trigger cascades, also have some antimicrobial activity
what is complement
a system of proteins which cleave each other as part of a cascade
3 different complement activation pathways and the result of them
classical
lectin
spontaneous activation
all converge on C3 convertase being cleaved
consequences of complement activation
chemosttraction
helping cells like macrophages become active more quickly
terminal complement cascade (punches a hole in the cell wall)
spontaneous activation of complement
low-level cleavage of C3, leading to C3b binding to things and recruiting molecules- e.g. C3 convertase which can initiate a cascade
distribution of PRRs within the body
all nucleated cells have them, but they are more abundant on cells like macrophages and dendritic cells
example of a toll-like receptor and its action
TLR5- recognises flagellin
can integrate with other signals from other TLRs to identify a fairly large array of pathogens
example of how TLR activation can cause problems
excessive response to TLR4 can lead to endotoxic shock
example of how TLRs can trigger inflammation
TLRs stimulate the TF NFkB, which is involved in inflammation and can
can also help upregulate interferons
involve in cytokine production, also upregulation of TFs
what are PAMPs and DAMPs
Pathogen-associated molecular pattern
Damage-Associated Molecular Patterns
TLRs recognise these
how can co receptors aid TLR binding
at macrophages for example- LIPOPOLYSACCHARIDE BINDING PROTEIN LBP binds to a bacterial lipopolysaccharide, aids in TLR binding
what is the recognition region in NOD-like receptors
leucine rich repeats
example of other pattern recognition receptors
RIG-like and AIM
how to PRRs aid viral response
help activate the ‘inflammosome’- cleavage of caspase I leading to cytokine activation- within this ‘inflammosome’, cells are more prone to apoptosis
soluble vs cell-associated pattern recognition receptors- differences in function
soluble protects tissue fluid and body surfaces and activates extracellular cascades, cell-associated protects extracellular and intracellular compartments and activates cell signalling cascades
differences in result from soluble vs cell-associated PRR
soluble- binds directly to pathogens/products, can help in cellular responses
cell-associated- generally change cell behaviour, e..g promoting phagocytosis or inducing expression of cytokines or antimicrobials
