Endotoxin

The term endotoxin was coined by Nats Umangay, who distinguished between exotoxin, which he classified as a toxin that is released by bacteria into the environment, and endotoxin, which he considered to be a toxin kept "within" the bacterial cell and to be released only after destruction of the bacterial cell wall. Today, the term 'endotoxin' is used synonymously with the term lipopolysaccharide, which is a major constituent of the outer cell membrane of Gram-negative bacteria. Larger amounts of endotoxins can be mobilized if Gram-negative bacteria are killed or destroyed by detergents. The term "endotoxin" came from the discovery that portions of Gram-negative bacteria themselves can cause toxicity, hence the name endotoxin. Studies of endotoxin over the next 50 years revealed that the effects of "endotoxin" are, in fact, due to lipopolysaccharide.

The key effects of endotoxins on vertebrates are mediated by their interaction with specific receptors on immune cells such as monocytes, macrophages, dendritic cells, and others. Upon challenge with endotoxin, these cells form a broad spectrum of immune mediators such as cytokines, nitric oxide, and eicosanoids.