CD14 gene provides instruction for making a surface antigen that is preferentially expressed on monocytes/macrophages.  This protein is an important player in host innate immunity; it mediates host defense against Gram-negative bacterial infections and also confers immunity against viral infections.  CD14 has a wide range of functions and associations; it binds to monomeric lipopolysaccharide and delivers it to the MD-2/TLR4 complex, thereby mediating the innate immune response to bacterial lipopolysaccharide (LPS).  It also acts via MyD88, TIRAP and TRAF6, leading to NF-kappa-B activation, cytokine secretion and the inflammatory response, and up-regulates cell surface molecules, including adhesion molecules.  It is expressed as either a 55 kDa membrane bound protein (mCD14), or as a 48 kDa soluble plasma protein (sCD14).

Mutations in CD14 are known to be associated with Crohn’s disease, decreased lung function, and hypercholesterolemia.