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Gastroenterology Research and Practice
Volume 2010 (2010), Article ID 240365, 8 pages
Review Article

Current Views of Toll-Like Receptor Signaling Pathways

Department of Microbiology and Immunology, Graduate School of Medicine and WPI Immunology Frontier Research Center, Osaka University, 2-2 Yamada-Oka, Suita, Osaka 565-0871, Japan

Received 16 March 2010; Accepted 15 September 2010

Academic Editor: Ekihiro Seki

Copyright © 2010 Masahiro Yamamoto and Kiyoshi Takeda. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


On microbial invasion, the host immediately evokes innate immune responses. Recent studies have demonstrated that Toll-like receptors (TLRs) play crucial roles in innate responses that lead not only to the clearance of pathogens but also to the efficient establishment of acquired immunity by directly detecting molecules from microbes. In terms of intracellular TLR-mediated signaling pathways, cytoplasmic adaptor molecules containing Toll/IL-1R (TIR) domains play important roles in inflammatory immune responses through the production of proinflammatory cytokines, nitric oxide, and type I interferon, and upregulation of costimulatory molecules. In this paper, we will describe our current understanding of the relationship between TLRs and their ligands derived from pathogens such as viruses, bacteria, fungi, and parasites. Moreover, we will review the historical and current literature to describe the mechanisms behind TLR-mediated activation of innate immune responses.