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Molecular Microbiology

**Figure 1:** Recognition of pathogens by the *PRR*. Various pathognes express *PAMP* which are recognised by *PRR*. This results in elaboration of *IL-1* and *TNF- $\ensuremath{\alpha}$* by the immune cell.
$\begin{figure}\centering \includegraphics{prrsignaling} \end{figure}$

Micro-organisms show pathogen-associated molecular patterns (PAMP) which are recognised by pathogen recognition receptors (PRR) in the host. An important recent discovery is that binding of lipo-polysaccharide or peptidoglycan to toll like receptors results in expression of cytokines such as inter-leukin one (IL-1) and tumor necrosis factor alpha (TNF- $\ensuremath{\alpha}$ ).

Organism	PAMP	PRR
Bacteria	Unmethylated CpG dinucleotides in bacterial DNA
Gram negative bacilli	LPS	TLR4
Mycobacteria	Glycolipids
Gram positive bacteria	Peptidoglycans	TLR2
Gram positive bacteria	Lipotechoic acids	TLR
Fungi	Mannans
Viri	Double stranded RNA

Subsections

LPS
TLR

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Adrian P. Ireland