CD14 is a glycosylphosphatidylinositol-linked glycoprotein that is preferentially expressed by mature cells of monocytic lineage (monocytes, macrophages, Langerhans cells) and follicular dendritic cells. Neutrophils exhibit lower levels of expression. This glycoprotein plays a key role in the innate immune response by recognizing and binding to lipopolysaccharides from Gram-negative bacteria, thereby facilitating the activation of the immune system.