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Recognition of Microorganisms (view source)
Revision as of 15:42, 13 August 2010
, 15:42, 13 August 2010Created page with "thumb|right|150px|Pattern Recognition Receptors - B. Catchpole, RVC 2008 * The innate immune system recognises components of pathogens which are intrinsically ..."
[[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:
**Lipopolysaccharides of gram-negative bacteria
**Peptidoglycans of gram-positive bacteria
**Mannose sugars
**D-isoform amino acids
*These are given away as foreign by expressing '''pathogen-associated molecular patterns''' (PAMPs)
* PAMPs are recognised by '''pattern recognition receptors''' (PRRs) expressed on mammalian cells
** Pattern recognition receptors are expressed on many different cell types, not just on phagocytes
** Not all are expressed by all cells: different cell types express a different range of PRRs
** PRRs are either intracellular, membrane-associated or soluble:
*** Recognition of pathogens via the cellular PRRs results in phagocytosis and inflammation
*** Recognition of pathogens via the humoral PRRs results in various killing mechanisms
* Engagement of PRRs by PAMPs triggers:
** '''Phagocytosis'''
** The expression of '''cytokines''', which brings about [[Inflammation - WikiBlood|inflammation]] and other immune responses
<big><center>'''''Examples of Pattern Recognition Receptors'''''</center></big>
{| style="width:60%; height:200px" border="1" align=center
!'''Receptor'''
!'''Location'''
!'''Ligands'''
|-
| TLR2 (''Toll-like receptor'')
| Cell Membrane
| Peptidoglycan of gram +ve bacteria
|-
| TLR3
| Cell Membrane
| dsRNA of RNA viruses (e.g. avian influenza)
|-
| TLR4
| Cell Membrane
| Lipoplysaccharide from gram-negative bacteria (e.g. E. coli, Salmonella)
|-
| TLR5
| Cell Membrane
| Bacterial flagellin
|-
| TLR9
| Cell Membrane
| Bacterial DNA (CpG DNA)
|-
| C-type lectins
| Soluble
| Carbohydrates, all bacteria, dead cells
|-
| fmlf
| Soluble
| Formyl peptides (i.e. all bacteria)
|-
| Complement receptors
| Soluble
| Fixed complement components (e.g. iC3b)
|-
| NOD2
| Cytoplasm
| Peptidoglycan of gram +ve bacteria
|-
| dsRNA-dependent Protein Kinase Receptor
| Cytoplasm
| ds RNA of RNA viruses
|}
[[Category:Innate Immune System]]
* The innate immune system recognises components of pathogens which are intrinsically foreign (i.e. not present on normal mammalian cells), such as:
**Lipopolysaccharides of gram-negative bacteria
**Peptidoglycans of gram-positive bacteria
**Mannose sugars
**D-isoform amino acids
*These are given away as foreign by expressing '''pathogen-associated molecular patterns''' (PAMPs)
* PAMPs are recognised by '''pattern recognition receptors''' (PRRs) expressed on mammalian cells
** Pattern recognition receptors are expressed on many different cell types, not just on phagocytes
** Not all are expressed by all cells: different cell types express a different range of PRRs
** PRRs are either intracellular, membrane-associated or soluble:
*** Recognition of pathogens via the cellular PRRs results in phagocytosis and inflammation
*** Recognition of pathogens via the humoral PRRs results in various killing mechanisms
* Engagement of PRRs by PAMPs triggers:
** '''Phagocytosis'''
** The expression of '''cytokines''', which brings about [[Inflammation - WikiBlood|inflammation]] and other immune responses
<big><center>'''''Examples of Pattern Recognition Receptors'''''</center></big>
{| style="width:60%; height:200px" border="1" align=center
!'''Receptor'''
!'''Location'''
!'''Ligands'''
|-
| TLR2 (''Toll-like receptor'')
| Cell Membrane
| Peptidoglycan of gram +ve bacteria
|-
| TLR3
| Cell Membrane
| dsRNA of RNA viruses (e.g. avian influenza)
|-
| TLR4
| Cell Membrane
| Lipoplysaccharide from gram-negative bacteria (e.g. E. coli, Salmonella)
|-
| TLR5
| Cell Membrane
| Bacterial flagellin
|-
| TLR9
| Cell Membrane
| Bacterial DNA (CpG DNA)
|-
| C-type lectins
| Soluble
| Carbohydrates, all bacteria, dead cells
|-
| fmlf
| Soluble
| Formyl peptides (i.e. all bacteria)
|-
| Complement receptors
| Soluble
| Fixed complement components (e.g. iC3b)
|-
| NOD2
| Cytoplasm
| Peptidoglycan of gram +ve bacteria
|-
| dsRNA-dependent Protein Kinase Receptor
| Cytoplasm
| ds RNA of RNA viruses
|}
[[Category:Innate Immune System]]