NEUTROPHILS RESPONDED TO IMMOBILIZED LIPOPOLYSACCHARIDE IN THE ABSENCE OF LIPOPOLYSACCHARIDE-BINDING PROTEIN

Lipopolysaccharide (LPS) in solution primes neutrophils for enhanced r elease of superoxide in response to N-formyl-methionyl-leucyl-phenylal anine. We show that LPS immobilized on polystyrene or polypropylene ac ted on neutrophils by a mechanism different from that of LPS in soluti on, Coating the surface with 1% plasma, either before coating with LPS (plasma/LPS) or after coating with LPS (LPS/plasma), was essential to induce the LPS response in neutrophils, However, plasma could. be rep laced by fibrinogen, type I collagen or type IV collagen, or to a less er extent, by fibronectin or vitronectin, which was not true for LPS i n solution. About 20% of the LPS added was immobilized on the plastic surfaces, based on its ability to adsorb anti-LPS antibody after exten sive washing, The amount of soluble LPS that might have been released from surfaces during the incubation with neutrophils was too low to ac count for the priming by immobilized LPS, About 13-20 min was needed f or neutrophils to become primed after incubation with immobilized LPS, immobilized LPS induced up-regulation of CD11b/CD18 and latent alkali ne phosphatase and also enhanced the adhesive response of neutrophils, Priming by immobilized LPS was inhibited by anti-CD14 antibody or by treatment of neutrophils with the LPS antagonist LA-14-PP. When immobi lized LPS was treated with anti-LPS-binding protein (LBP) antibody, tb e response of neutrophils to LPS/plasma was inhibited but the response to plasma/LPS or fibrinogen/LPS was not. Thus, the LPS in plasma/LPS or fibrinogen/LPS acted on neutrophils iu an LBP-independent manner. W e conclude that the CD14-dependent LPS receptor system of neutrophils was capable of working in the absence of LBP, hut only when LPS was im mobilized on a surface coated with protein.