In monocytes, macrophages, and neutrophils, the synthesis and expression of CD14 can be regulated and changed by different media, such as TNF in neutrophils- α、 G-CSF, formyl methionyl-leucyl-phenylalanine (f-MLP) and LPS can increase the expression of CD14 to about 2 times. In monocytes, the anti-inflammatory factors IL-4 and IL-13 can reduce the expression of CD14 at the transcription level in 24-48 hours. INF- α， INF- γ、 IL-2, and TGF- β It can induce the rapid down-regulation of CD14 expression, and the ligand LPS of CD14 can also change the number of CD14 molecules on monocytes. In different cell types, cultured with different endotoxin concentrations and incubation times, the expression results of the CD14 molecule were also inconsistent. After stimulation of monocytes with LPS for 30~180 min, the expression of CD14 showed a rapid up-regulation of 50%~100%; Then, after 3~6 hours, the expression of CD14 was downregulated to 50%~75%; After 1~6 days, it was significantly increased to 200%~300%. The first rapid rise of CD14 was the result of intracellular translocation of the CD14 molecular pool, and the second rise was related to protein biosynthesis and monocyte differentiation.

CD14 is a pattern recognition molecule of myeloid cells. In addition to LPS, some host molecules and other bacterial molecules can also bind to CD14 molecules of myeloid cells and can induce the activation of transcription factors. These molecules include phosphatidylinositides, LAM of Mycobacterium tuberculosis, acyl poly galactoside of Klebsiella pneumonia, a polychronic acid polymer of Pseudomonas, a rhamnose-galactose polymer of Streptococcus, peptidoglycan of PGN, lipocytes acid, Bacillus dermatitis, W1 surface antigen of yeast, borrelia, Treponema pallidum The outer membrane lipoproteins and lipopeptides of Bacteroides fragilis, the chitin of arthropods, the cell extracts of gram-positive bacteria, the heat shock protein 70 (hsp70) of the host, and apoptotic bodies. In addition, LAM can also stimulate undifferentiated THP-1 cells to produce NF in the presence of recombinant sCD14 or recombinant LBP- κ B translocation, cells without CD14 expression and PGN non-responsive cells can become PGN sensitive cells after transfection of the CD14 molecule.

The above CD14 ligand molecules are highly conserved molecules with similar structural characteristics and can be recognized by the same receptors, such as CD14 molecules and TLR of myeloid cells. Although these common binding receptors are CD14, in terms of LPS and LPS-like ligands, there may be differences in other CD14 binding signal transduction molecules, such as TLR4 for LPS receptor, TLR2 for lipoprotein receptor, and TLR9 for CpG receptor in bacterial DNA.