Toll-like Receptors and Innate Immunity

ABSTRACT

Toll-like receptors (TLRs) are the best-characterized membrane-bound receptors in innate immune cells, including macrophages and dendritic cells. Upon recognition of specific ligands originating from pathogen- and modified self-derived molecules, TLRs trigger intracellular signaling cascades that involve various adaptor proteins and enzymes, resulting in the generation of proinflammatory and antimicrobial responses through the activation of transcription factors such as nuclear factor-kappaB. TLR-dependent signaling pathways are tightly regulated during innate immune responses by a variety of negative regulators. This review focuses on the newly described regulation of TLR-dependent signaling pathways, and emphasizes the roles of TLRs in innate immunity. Efforts to modulate these regulatory pathways and signaling molecules may result in the development of new therapeutic strategies through TLR-based therapy.