Bacterial Lipopolysaccharides: Chemical Constitution, Endotoxic Activity, and Biological Neutralization

In 1892, Richard Pfeiffer, a student of Robert Koch, was the first to describe bacterial endotoxins as heat-stable, cell-associated components of Vibrio cholerae which induced toxic reactions in guinea pigs [1]. He clearly distinguished these substances from the already known heat-labile exotoxins which are actively secreted by pathogenic bacteria [2]. Today we know that endotoxins structurally consist of a lipid and a carbohydrate component and, thus, constitute lipopolysaccharides (LPS). Therefore, both terms endotoxin and LPS are used as synonyms.