CD14

CD14 (cluster of differentiation 14) is a surface membrane protein made mostly by macrophages as part of the innate immune system. It helps to detect bacteria in the body by binding lipopolysaccharide (LPS), a pathogen-associated molecular pattern (PAMP). It is highly expressed on monocytes and macrophages, and at lower levels on neutrophils and dendritic cells. CD14 exists in two forms, one anchored to the membrane by a glycosylphosphatidylinositol (GPI) tail (mCD14), the other a soluble form (sCD14). Soluble CD14 either appears after shedding of mCD14 (48 kDa) or is directly secreted from intracellular vesicles (56 kDa). The x-ray crystal structure of human CD14 reveals a monomeric, bent solenoid structure containing a hydrophobic amino-terminal pocket.