Lipopolysaccharide binding protein (LBP)
Lipopolysaccharide binding protein (LBP) in serum or plasma, as an aid in the diagnosis and prognosis of diseases that are induced by exposure to endotoxin, such as sepsis and infectious complications of surgery and trauma.
Endotoxins (lipopolysaccharides and lipooligosaccharides; LPS and LOS) produced by gram-negative bacteria represent potent triggers of the inflammatory response, stimulating the production of proinflammatory cytokines (eg., IL-6, TNF, IL-8) by monocytes, endothelial cells, granulocytes and lymphocytes. The recognition of LPS by effector cells is greatly enhanced through the function of lipopolysaccharide binding protein (LBP), an acute phase protein that binds and recruits the endotoxin to the surface of these cells. LBP is structurally related to the bactericidal/permeability-increasing protein (BPI), a glycoprotein produced in the azurophilic granules of polymorphonuclear leukocytes that kills bacteria and neutralizes as well as clears endotoxin.
Due to its critical position in the early response to bacteria and endotoxin, the plasma levels of LBP have been investigated in numerous human populations. In normal individuals, LBP is present in plasma at concentrations between 2 and 10 μg/mL. In some patient populations, LBP levels can exceed 100 μg/mL and may persist for several days. Elevated plasma levels of LBP have been reported in patients with sepsis, abdominal infections, meningococcemia, SIRS, ulcerative colitis, Crohn's disease, hemolytic uremic syndrome, and cardiopulmonary bypass patients. Injection of endotoxin into healthy volunteers also causes a rise in LBP levels, and longitudinal sampling from liver surgery patients or patients with hemorrhage due to trauma also show elevated LBP levels within 24 hours of the original insult. LBP levels do not appear to be elevated in patients with inflammatory disorders. For these reasons, it has been suggested that LBP levels may be indicative of exposure to bacteria or endotoxin and prognostic of disease progression, and may provide a new tool for monitoring patient therapy and long-term patient management.
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