Innate immune sensing and its roots: the story of endotoxin.

How does the host sense pathogens? Our present concepts grew directly from longstanding efforts to understand infectious disease: how microbes harm the host, what molecules are sensed and, ultimately, the nature of the receptors that the host uses. The discovery of the host sensors--the Toll-like receptors--was rooted in chemical, biological and genetic analyses that centred on a bacterial poison, termed endotoxin.