Lipopolysaccharide (LPS)-Specific Monoclonal Antibodies Regulate LPS Uptake and LPS-Induced Tumor Necrosis Factor-  Responses by Human Monocytes

Abstract

Lipopolysaccharide (LPS)-monocyte/macrophage interactions are central to the infected host's inflammatory response to gram-negative bacteria. Flow cytometry was used to analyze the regulation by LPS-specific monoclonal antibodies (MAbs) of fluorescein isothiocyanate-conjugated LPS uptake by human peripheral blood monocytes. The uptake of LPS was stimulated by fresh or heat-inactivated serum (NHS or delta NHS) or by LPS-binding protein and inhibited by alpha-LPS or alpha-CD14 (LPS receptor) MAbs. The inhibition of alpha-LPS uptake was offset in the presence of NHS by a simultaneous MAb-mediated increase in LPS uptake that was blocked by alpha-complement receptor 1. Monocyte tumor necrosis factor-alpha responses to LPS were augmented by NHS and delta NHS and inhibited by alpha-LPS MAbs. Thus, alpha-LPS MAbs down-regulate the proinflammatory uptake of LPS by human monocytes via membrane-bound CD14 while promoting complement-mediated opsonic uptake through membrane-associated CR1.

Cathelicidin Family of Antibacterial Peptides CAP18 and CAP11 Inhibit the Expression of TNF-α by Blocking the Binding of LPS to CD14+ Cells

“…Thus, a drug that suppresses the actions of LPS could be a reasonable additional therapy for endotoxin shock or sepsis caused by Gram-negative bacterial infections. Until now, several strategies, including neutralizing Abs against LPS, LBP, or cytokines, have been tested to prevent the cascade of LPS-induced inflammatory reactions (2,25,(35)(36)(37). Recently, however, much attention has focused on the low m.w.…”

“…Moreover, we have argued in this study that CAP18 and CAP11 could bind to LPS and CD14 and neutralize the activities of LPS. To suppress the cascade of LPS-induced inflammatory reactions, several agents, including neutralizing Abs against LPS, LBP, or cytokines, have been examined (2,25,(35)(36)(37). Unlike these agents, CAP18 and CAP11 would be expected not only to block the onset of LPS-triggered inflammatory reactions by binding directly to LPS and CD14, but also to overcome the underlying Gram-negative bacterial infections in the septic shock syndrome.…”

Influence of Synthetic Antiendotoxin Peptides on Lipopolysaccharide (LPS) Recognition and LPS-Induced Proinflammatory Cytokine Responses by Cells Expressing Membrane-Bound CD14

“…FITC-conjugated LPS was prepared as previously described (20,28). FITC-LPS conjugates typically contained 2 to 10 mg of FITC/mg of LPS.…”

“…The signaling unit of the LPS receptor is comprised of members of the Toll-like receptor family of transmembrane proteins characterized by their amphiphilic properties and leucine-rich repeats (31, 36). Serum-associated LPS-binding protein (LBP), which forms complexes with LPS through high-affinity attachment to the lipid A moiety, catalyzes LPS recognition by mCD14, resulting in the generation of LPS-induced proinflammatory signals (12,14).Recent experiments have attempted to define the roles of mCD14 and LBP in LPS-related septic events as well as the possible protective or therapeutic activities of proteins, including antibodies, that neutralize LPS by interrupting its proinflammatory interactions with mCD14 and LBP.We previously showed that LPS-specific monoclonal antibodies (MAbs) are capable of neutralizing cytokine-and transcription factor-inducing activities of LPS by inhibiting the binding of LPS to mCD14 expressed on human peripheral blood monocytes (PBMC) and on CD14-transfected Chinese hamster ovary fibroblasts (CHO-CD14 cells) (20,21).Polymyxin B (PMB), a cationic, cyclic peptide antibiotic, inhibits biological activities of LPS through high-affinity bind-* Corresponding author. Mailing address:…”

“…We previously showed that LPS-specific monoclonal antibodies (MAbs) are capable of neutralizing cytokine-and transcription factor-inducing activities of LPS by inhibiting the binding of LPS to mCD14 expressed on human peripheral blood monocytes (PBMC) and on CD14-transfected Chinese hamster ovary fibroblasts (CHO-CD14 cells) (20,21).…”