lipopolysaccharidiques

Lipopolysaccharides (LPS), also known as endotoxins, are large molecules consisting of a lipid and a polysaccharide. They are found in the outer membrane of Gram-negative bacteria. LPS plays a crucial role in the structural integrity of the bacterial outer membrane and also acts as a potent immunostimulant.

The LPS molecule is composed of three distinct regions: lipid A, the core polysaccharide, and the O antigen. Lipid A is the hydrophobic anchor embedded within the bacterial membrane and is responsible for the endotoxic properties of LPS. The core polysaccharide links lipid A to the O antigen and contains various sugars. The O antigen is a variable polysaccharide chain that extends outward from the bacterial surface and is highly antigenic, meaning it can elicit an immune response. This variability in the O antigen is often used for bacterial serotyping.

In the context of infection, the presence of LPS from Gram-negative bacteria can trigger a strong inflammatory response in the host. This response is mediated by immune cells recognizing LPS through specific receptors like Toll-like receptor 4 (TLR4). While this response is crucial for fighting bacterial infections, excessive or uncontrolled inflammation caused by LPS can lead to serious conditions such as sepsis, a life-threatening systemic inflammatory response. Due to its potent biological activity, LPS is a significant subject of study in immunology, microbiology, and medicine.