Mammalian toll-like receptors

Objective: To review the role of mammalian Toll-like receptors (TLRs) in host defense. Date Sources: MEDLINE search and current literature. Results: First, TLRs participate in the recognition of molecular patterns present on microorganisms. Second, TLRs are expressed at the interface with the environment, the site of microbial invasion. Third, activation of TLRs induces expression of costimulatory molecules and the release of cytokines that instruct the adaptive immune response. Fourth, activation of TLRs leads to direct antimicrobial effector pathways that can result in elimination of the foreign invader. Conclusions: Maintained throughout evolution, mammalian TLRs are proteins that participate in innate immunity to microbial pathogens. Insights into TLR activation pathways provide new therapeutic targets for intervention in infectious and immunologic disease.