The human CD14 gene is located on chromosome 5 at 5q23-31. According to the cDNA sequence of CD14, CD14 is composed of 356 amino acids. After the polypeptide is synthesized in the ribosome, it is transported to the Golgi complex for glycosylation reaction, so CD14 is a glycoprotein. The N-terminal lead peptide of CD14 consists of 19 amino acids and is an intron composed of 88 bases after the start of the ATG codon. The DNA sequence of CD14 contains two exons, encoding a single 1.4kb mRNA transcript, and the translated protein contains several leucine-rich repeats (LRR) motifs. Its C-terminal leading sequence is composed of 28~30 amino acids. It is further processed in the Golgi complex, added with the phosphatidylinositol (PI) group, and undergoes a saccharification reaction. After maturing, it is secreted onto the cell membrane to form membrane CD14 (mCD14). MCD14 is anchored on the cell membrane by the tail of phosphatidylinositol. After translation, PI is saccharified to produce the anchoring molecule of phosphatidylinositol (GPI). Therefore, CD14 is not a transmembrane protein but is attached to the cell membrane through the tail of GPI. The C-terminal contains 17 hydrophobic amino acids, neutral amino acids, and N-linked glycosylation potential sites. The relative molecular weight of CD14 after saccharification is about 55000. Although there is only one CD14 transcript, according to the antigenicity of CD14, the binding ability of LPS, and the sensitivity of enzyme digestion, there should be different surface expressions of CD14 molecules on the cell membrane.

At first, it was confirmed that CD14 was a myeloid differentiation antigen and existed in mature medullary cells, while immature medullary cells did not have CD14. The differentiation of immature leukemia cells can promote the expression of the CD14 molecule, so the CD14 molecule can be used as a marker of cell differentiation, and CD14 can assist in the diagnosis of acute myeloid leukemia. CD14 is highly conserved in different species, for example, the homology of the rabbit CD14 gene with human and mouse CD14 is 73% and 64% respectively. The Human CD14 gene is located on chromosome 5, and the mouse CD14 gene is located on chromosome 8. In the specific gene region of human CD14 gene clusters, other growth factors and receptors are also encoded, such as IL-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF), platelet-derived growth factor (PDGF) β- Adrenal receptor, etc.

CD14 exists on the surface of different myeloid cells, and is abundant in monocytes, macrophages, neutrophils, and dendritic cells, while it is extremely low in B cells, basophils, breast cells, placental trophoblast cells, and gingival fibroblasts. The number of CD14 molecules is about 3000 in human neutrophils, but there are different reports in monocytes, including 600029000, 40-45000114000115000, and even 190000. However, about 10% of monocytes expressed CD14 molecule, and the expression of CD11b and CD33 was also low, while the expression of CD16, HLA-DR, intercellular adhesion molecule-1 (ICAM-1), and very late antigen-4 (VLA-4) was significantly up-regulated.

When monocytes differentiate into macrophages in different tissues, the expression of CD14 is also accompanied by changes, such as increased expression of CD14 in macrophages in the abdominal cavity, thoracic cavity, and extravascular brain; The expression of CD14 decreased in alveolar macrophages, small ganglion cells, liver macrophages, and intestinal mucosal macrophages.