Toll-like Receptors and Sepsis.

Recent evidence suggests that Toll-like receptors (TLRs) play a major role in innate immunity to recognize specific molecular patterns derived from pathogens, including lipid, protein, DNA, and RNA, and to fight against pathogens. Each TLR displays a difference in the expression pattern, intracellular localization, and signaling pathway, resulting in the distinct immune responses. The resultant immune activation augments host resistance to a variety of infectious organisms. However, such responses may exceed the threshold to maintain host homeostasis in the case of sepsis. TLR-mediated innate immune activation also induces several molecules shown to negatively regulate TLR signaling. Thus, TLRs may play an important role in positive and negative regulation of immune responses during sepsis.