CD14

Cluster of differentiation 14 (CD14), is a cell surface glycoprotein, and is a is a component of the innate immune system. CD14 is a myelomonocytic differentiation antigen preferentially expressed on monocytes, macrophages, and activated granulocytes. CD14 exists in two forms. Either it is anchored into the membrane by a glycosylphosphatidylinositol tail (mCD14) or it appears in a soluble form (sCD14). Soluble CD14 either appears after shedding of mCD14 (48 kDa) or is directly secreted from intracellular vesicles (56 kDa). CD14 acts as a co-receptor (along with the Toll-like receptor TLR 4 and MD-2) for the detection of bacterial lipopolysaccharide (LPS). CD14 can bind LPS only in the presence of lipopolysaccharide-binding protein (LBP). CD14 has been proposed to be involved in various biological processes, including transportation of other lipids, cell-cell interaction during different immune responses, as well as recognition of apoptotic cells. Although LPS is considered its main ligand, CD14 also recognizes other pathogen-associated molecular patterns. CD14+ cells are monocytes that can differentiate into a host of different cells. CD14 has been shown to interact with Lipopolysaccharide-binding protein.