The immune system consists of adaptive immunity and innate immunity. Lymphocytes are key players in the former, whereas macrophages and dendritic cells have important roles in innate immunity. Macrophages and dendritic cells employ pathogen sensors for sensing microbial organism. Toll-like receptors (TLR)belong to the pathogen sensors in innate immunity. TLRs respond to microbial glycolipids, proteins, and nucleic acid, triggering innate immune responses. Recently, TLRs are reported to respond to self-derived products and have a role in non-infectious inflammatory diseases like autoimmune disease, allergy, obesity,and atherosclerosis. Our division focuses on molecular mechanisms underlying pathogens sensing by TLRs, and those regulating TLR signaling. Dysregulation of these mechanisms would lead to inflammatory diseases. Our goal is to understand molecular basis of the innate immune system.