EVIDENCE THAT THE RECEPTOR FOR SOLUBLE CD14-LPS COMPLEXES MAY NOT BE THE PUTATIVE SIGNAL-TRANSDUCING MOLECULE ASSOCIATED WITH MEMBRANE-BOUND CD14

Membrane-bound CD14 acts as a receptor for lipopolysaccharide (LPS) on monocytes/macrophages and neutrophils. Studies have suggested that th e activation of monocytes/macrophages by the binding of LPS to membran e-bound CD14 may require the association of a signal-transducing molec ule with membrane-bound CD14. The observation that non-CD14 expressing cells, such as endothelial cells, san nevertheless be activated by a complex of LPS and a soluble form of CD14 (sCD14) suggests that the re ceptor for this complex may be identical to the signal transducing mol ecule associated with membrane-bound CD14. The studies described show that two CD14-specific MoAb are able to block the LPS-induced activati on of endothelial cells but do not affect the response of monocytes to LPS. This suggests that the interaction of the sCD14:LPS complex with endothelial cells is distinct from the interaction of membrane-bound CD14 with its putative signal-transducing molecule.