Lipopolysaccharide

Lipopolysaccharide (LPS) is a heat-stable endotoxin from the outer layer of the cell envelope of Gram-negative bacteria. LPS is composed of the lipid A. the nuclear polysaccharide (core) and an O-specific polysaccharide component.

LPS represents an important virulence factor after it has entered the body. LPS causes toxic and pyrogenic effects (exogenous pyrogens). Furthermore, LPS influences the natural immunity, especially by activating the complement and coagulation system.

Lipopolysaccharides are recognised and bound by LPS receptors on macrophages. LPS is one of the strongest macrophage activators and induces the production of cytokines (interferon-alpha, interleukin-6, interleukin-1).

LPS can be recognized by certain T cells in conjunction with CD1 (lipid antigen CD1 presentation pathway). CD1-glycoproteins belong to the so-called MHC-like molecules. Their structure strongly resembles MHC-1 complexes.

Furthermore, LPS has a mitogenic activity for B-lymphocytes and induces the formation of antibodies. A high concentration of LPS, as it occurs in sepsis, leads to endotoxin shock (septic shock). Experimentally, LPS produces the Sanarelli-Shwartzman reaction.