CD14 （cluster of differentiation 14） is a human 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）. 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）.