[Bacterial infections and toll-like receptors]

Toll-like receptors are type-1 transmembrane receptors involved in microbial recognition. TLR4 has been shown to function as the lipopolysaccharide signaling receptor, while TLR2 recognizes peptidoglycans from Gram-positive bacteria, and lipoproteins. TLR9 is involved in the recognition of bacterial DNA (CpG DNA). Although various microbial cell wall components are recognized by different receptors, all of these responses are abrogated in MyD88-deficient cells. These results show that different TLRs recognize different microbial cell wall components, and that MyD88 is an essential signaling molecule shared among interleukin-1 receptor/Toll family members. However, in LPS signaling MyD88-independent pathway is present in addition to MyD88-dependent pathway.