lipopolysakkaridien

Lipopolysaccharides (LPS), also known as endotoxins, are large molecules consisting of a lipid and a polysaccharide found in the outer membrane of Gram-negative bacteria. They play a crucial role in the structural integrity of the bacterial cell wall and also contribute to the pathogenicity of these bacteria. LPS is composed of three main components: lipid A, a core oligosaccharide, and an O-antigen polysaccharide chain. Lipid A is the hydrophobic anchor that embeds the LPS in the bacterial outer membrane. The core oligosaccharide is a conserved structure linked to lipid A, and it can extend outwards. The O-antigen is a variable polysaccharide chain that faces the external environment and is responsible for the serological diversity of Gram-negative bacteria.

When Gram-negative bacteria are lysed or their cell walls are damaged, LPS is released into the surrounding environment. Lipid A, in particular, is a potent immunostimulant. It binds to specific receptors on immune cells, such as Toll-like receptor 4 (TLR4), initiating a strong inflammatory response. This response can be beneficial in fighting infection, but excessive or uncontrolled inflammation triggered by LPS can lead to severe pathologies, including septic shock, a life-threatening condition characterized by widespread inflammation, low blood pressure, and organ damage. The endotoxic activity of LPS means that even dead Gram-negative bacteria can cause harm. Its presence is a key factor in the immune system's recognition and response to Gram-negative bacterial infections.