CD14 is a single copy gene encoding 2 protein forms: a 50 to 55 kDa glycosylphosphatidylinositol anchored membrane protein (mCD14) and a monocyte or liver derived soluble serum protein (sCD14) that lacks the anchor. Both molecules are critical for lipopolysaccharide (LPS) dependent signal transduction，and sCD14 confers LPS sensitivity to cells lacking mCD14. Increased sCD14 levels are associated with inflammatory infectious diseases and high mortality in gram negative shock. CD14 also appears to be involved in clearance of gram-negative bacteria via its high affinity binding to LPS-LPB complexes.