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| | =Actions of the Innate Immune System= | | =Actions of the Innate Immune System= |
| − | ==Recognition of Microorganisms== | + | ==[[Recognition of Microorganisms]]== |
| − | [[Image:PRRs.jpg|thumb|right|150px|Pattern Recognition Receptors - B. Catchpole, RVC 2008]] | |
| − | * The innate immune system recognises components of pathogens which are intrinsically foreign (i.e. not present on normal mammalian cells), such as:
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| − | **Lipopolysaccharides of gram-negative bacteria
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| − | **Peptidoglycans of gram-positive bacteria
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| − | **Mannose sugars
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| − | **D-isoform amino acids
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| − | *These are given away as foreign by expressing '''pathogen-associated molecular patterns''' (PAMPs)
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| − | * PAMPs are recognised by '''pattern recognition receptors''' (PRRs) expressed on mammalian cells
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| − | ** Pattern recognition receptors are expressed on many different cell types, not just on phagocytes
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| − | ** Not all are expressed by all cells: different cell types express a different range of PRRs
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| − | ** PRRs are either intracellular, membrane-associated or soluble:
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| − | *** Recognition of pathogens via the cellular PRRs results in phagocytosis and inflammation
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| − | *** Recognition of pathogens via the humoral PRRs results in various killing mechanisms
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| − | * Engagement of PRRs by PAMPs triggers:
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| − | ** '''Phagocytosis'''
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| − | ** The expression of '''cytokines''', which brings about [[Inflammation - WikiBlood|inflammation]] and other immune responses
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| − | | |
| − | | |
| − | <big><center>'''''Examples of Pattern Recognition Receptors'''''</center></big>
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| − | | |
| − | {| style="width:60%; height:200px" border="1" align=center
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| − | | |
| − | !'''Receptor'''
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| − | !'''Location'''
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| − | !'''Ligands'''
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| − | |-
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| − | | TLR2 (''Toll-like receptor'')
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| − | | Cell Membrane
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| − | | Peptidoglycan of gram +ve bacteria
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| − | |-
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| − | | TLR3
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| − | | Cell Membrane
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| − | | dsRNA of RNA viruses (e.g. avian influenza)
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| − | |-
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| − | | TLR4
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| − | | Cell Membrane
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| − | | Lipoplysaccharide from gram-negative bacteria (e.g. E. coli, Salmonella)
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| − | |-
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| − | | TLR5
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| − | | Cell Membrane
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| − | | Bacterial flagellin
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| − | |-
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| − | | TLR9
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| − | | Cell Membrane
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| − | | Bacterial DNA (CpG DNA)
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| − | |-
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| − | | C-type lectins
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| − | | Soluble
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| − | | Carbohydrates, all bacteria, dead cells
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| − | |-
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| − | | fmlf
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| − | | Soluble
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| − | | Formyl peptides (i.e. all bacteria)
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| − | |-
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| − | | Complement receptors
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| − | | Soluble
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| − | | Fixed complement components (e.g. iC3b)
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| − | |-
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| − | | NOD2
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| − | | Cytoplasm
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| − | | Peptidoglycan of gram +ve bacteria
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| − | |-
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| − | | dsRNA-dependent Protein Kinase Receptor
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| − | | Cytoplasm
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| − | | ds RNA of RNA viruses
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| − | |}
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| | ==Phagocytosis== | | ==Phagocytosis== |