CD14 is an acute phase glycoprotein that binds lipopolysaccharide endotoxins (LPS) from Gram-negative bacteria. It is primarily expressed on monocytes, macrophages, and neutrophils, and soluble forms can be secreted or shed from the cell surface. CD14 accepts LPS from its initial binding by LBP, and it can further transfer LPS to the TLR4/MD2 complex. LPS acctivation of TLR4 triggers inflammatory activation. CD14 also contributes to the response to TLR3 ligands, phosphoinositides, as well as the surfactant proteins SP-A and SP-D.