Bacterial Endotoxin: Chemical Constitution, Biological Recognition, Host Response, and Immunological Detoxification

The discovery of endotoxin dates from the late nineteenth century when Richard Pfeiffer, then working in Berlin, characterized endotoxins as heat-stable and cell-associated molecules (Westphal et al. 1977), thus distinguishing them from the heat-labile and proteinous exotoxins which are actively secreted by bacteria (Bhakdi et al. 1994). They were first found to be produced by Vibrio cholerae bacteria and later by Salmonella and Serratia. Endotoxins, due to their various potent biological activities soon attracted worldwide scientific interest. Initial chemical analyses of purified endotoxin indicated that it consists essentially of polysaccharide and lipid, and it was therefore termed lipopolysaccharide (LPS). Today the terms endotoxin (Wolff 1904) and lipopolysaccharide (Shear and Turner 1943) are used synonymously for the same molecule.