Mouse CD14 DuoSet ELISA

CD14 cooperates with another acute phase protein, LBP (LPS-binding protein), which binds LPS and transfers it to CD14 (1-3, 17). LPS can be further transferred from CD14 to the TLR4/MD2 complex on the cell surface (1). LPS causes signaling via clustering of LPS-bound CD14/TLR4/ MD2 complexes within cholesterol-rich lipid rafts (1). These signals induce production of inflammatory cytokines and other inflammatory proteins (18, 19). When uncoordinated, the signals contribute to septic shock (1). CD14 potentiates TLR-mediated signals triggered by microbe-derived ligands other than LPS, including TLR2 activation by polymeric peptidoglycan, gram-positive bacterial lipoteichoic acid, or mycobacterial lipoarabinomannan (1, 20). It increases uptake and trafficking of the viral TLR3 ligand, poly(I:C) (1, 20). In the lungs, CD14 binds phosphoinositides and surfactant proteins, such as SP-A and SP-D, via interaction of lipids with the CD14 LPS binding site (21, 22). CD14 may also bind ICAM-3 on apoptotic leukocytes and induce phagocytosis (23).  

High concentrations of sCD14 may inhibit LPS-mediated responses by competing for binding to mCD14 (24). In the presence of LBP, however, sCD14 can also potentiate LPS responses or help cells to clear circulating LPS, whether or not the cells express mCD14 (16-19). At low concentrations of LPS, both sCD14 and mCD14 can mediate endothelial cell responses such as upregulation of E-selectin, while response to intermediate concentrations of LPS requires mCD14 (16). Circulating sCD14, especially presepsin, is increased in sepsis and may correlate with severity (11, 12). sCD14 may be increased as compared to normal circulating sCD14 in some autoimmune diseases, such as multiple sclerosis and rheumatoid arthritis, but decreased in others, such as Crohn's disease (25-27). sCD14 can also modulate inflammation-driven insulin resistance (28).