Endotoxiinit

Endotoxiinit, in microbiology, are lipopolysaccharide molecules that form part of the outer membrane of most Gram-negative bacteria. They constitute a type of endotoxin, in contrast to exotoxins, which are secreted proteins.

Structure and components: Endotoxins consist of lipid A, a core oligosaccharide, and a variable O antigen. Lipid A is the principal toxic moiety and drives the majority of the inflammatory response in animals.

Release and stability: Endotoxins are released upon bacterial lysis or growth and can persist in the environment and in pharmaceutical preparations. They are heat-stable and resistant to many common disinfectants, making decontamination challenging.

Mechanism of action and effects: Endotoxins activate the host immune system through the TLR4 receptor complex (CD14, MD-2, and LBP), triggering the production of pro-inflammatory cytokines such as TNF, IL-1, and IL-6. This can lead to fever, leukocytosis, hypotension, and in severe cases septic shock.

Clinical and industrial relevance: Endotoxin contamination is a major safety concern for vaccines, injectable medicines, and medical devices. Detection relies on assays like the Limulus amebocyte lysate (LAL) test or recombinant Factor C. Removal and inactivation methods include depyrogenation (dry heat treatment), ultrafiltration, and various chromatography techniques.