NLRs have been found to be involved in cytosolic recognition of microbial molecules such as PGN derivatives (by NOD1 and NOD2) and flagellin (by NLRC4/IPAF) [3].
Innate immune host responses are rapidly initiated following the recognition of microbial molecules such as endotoxin, peptidoglycan, lipoteichoiec acid, lipopeptides, zymosan and nucleic acids expressing pathogen associated molecular patterns (PAMPs) or endogenous "danger" molecules (DAMPS) release by damaged cells [5], [6].
TLR2 recognizes a wide array of microbial molecules such as peptidoglycan and lipoteichoic acid and mediates the immune response to numerous bacteria and fungi.
These include an avoidance behaviour, triggered by the detection of specific microbial molecules, such as the cyclic pentadepsipeptide biosurfactant serrawettin W2, produced by some strains of Serratia marcescens (Pradel et al., 2007).
PRRs include Nod-like receptors (NLRs), which mediate cytosolic recognition of microbial molecules and promote their clearance [ 7– 9], and Toll-like receptors (TLRs), which are located at the cell surface or within endosomal membranes and recognize a wide range of microbial molecules such as lipopolysaccharide (LPS), peptidoglycan, lipoteichoic acid, flagellin, and zymosan [ 8, 10, 11].
Immature Langerhans' cells protect against HIV-1 infection by internalizing and degrading HIV-1 viral particles and inhibiting T-cell infection [13], but Langerhans' cells activated through exposure to microbial-associated inflammatory molecules such as lipopolysaccharide (LPS), TNF-α, and Toll-like receptor 2 (TLR2) agonists are efficient mediators of HIV-1 trans-infection [14] [16].
Moreover, γδ T cells can also recognize non-peptide molecules, such as microbial metabolites (pyrophosphomonoesters and alkyl amines) [ 4, 5] and synthetic aminobisphosphonates (pamidronate) [ 6] directly via TCRγδ.
Scavenger receptors bind and internalize exogenous and endogenous damage-associated molecules such as microbial lipopolysaccharide and lipoteichoic acid, anionic phospholipids, beta amyloid peptide, modified low density lipoprotein (LDL), and advanced glycation end products [ 12].
Toll-like receptors (TLRs) can recognize microbial patterns and utilize adaptor molecules, such as-MyD88 or (TRIF TIR-domain-containing adapter-inducing interferon-β), to initiate downstream signaling that ultimately affects the initiation of adaptive immunity.
We identified a large number of genes encoding proteins with established functions in immunity related sensing of microbial signatures and signaling, as well as effector molecules such as antimicrobial peptides and inhibitors of microbial proteinases.
Furthermore, it has also been associated with the accumulation of small signaling molecules, such as ppGpp, microbial hormones, and late intermediates or end-products of the secondary metabolite biosynthetic pathways Ruiz et al. 2008; O'Rourke et al. 2009; Hsiao et al. 2009; Wang et al. 2009.
