The primary defensive cells in innate immune response are the Professional phagocytes. Macrophages, neutrophils and dendritic cells are called professional phagocytes.
The
innate immune system relies on a large family of pattern recognition receptors
(PRRs), which detect distinct evolutionarily conserved structures on pathogens,
termed pathogen-associated molecular patterns (PAMPs).
Upon PAMP recognition, PRRs activation transmits intracellular signal activating a multitude of intracellular signaling pathways, ultimately result in the activation of gene expression and synthesis of a broad range of molecules, including cytokines, chemokines, cell adhesion molecules, and immunoreceptors which together clear out the pathogen from the system or can activate adaptive immune response.
PRRs |
PAMPs |
Present on the
innate immune cells as cell surface receptors or cytosolic PRRs |
Are evolutionary
conserved structures on pathogens |
PRRs can
distinguish self cells and non self cells by recognizing PAMPs |
PAMPs are ‘signatures’
present only on pathogen |
PRRs are generally
glycoproteins |
PAMPs can be
carbohydrate, protein or even nucleic acids of bacteria and virus |
PRRs include Toll
like receptors (TLRs) TLRs
are membrane-bound receptors localized at the cellular or endosomal membranes |
PAMPs include flagellin
protein that makes bacterial flagella, lipopolysaccharide layer of gram
negative bacteria, peptidoglycan of bacterial cell wall, zymozan of yeast
cell wall, nucleic acids of both bacteria and viruses. |
Cytosolic PRRs, include
retinoid acid-inducible gene I (RIG-I)-like receptors (RLRs) (393) and
nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) |
Nucleic acids of
virus and bacteria generally interacts with cytosolic PRRs |
Some examples of
PRRs and PAMPs interaction
|
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