Worthen G S, Avdi N, Vukajlovich S, Tobias P S
Department of Medicine, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
J Clin Invest. 1992 Dec;90(6):2526-35. doi: 10.1172/JCI116146.
Endotoxemia results in neutrophil localization within a number of microcirculatory beds, reflecting in part an adhesive interaction between neutrophils and the vascular endothelial cell. In previous studies, endotoxin or lipopolysaccharide (LPS) treatment of rabbits resulted in neutrophil sequestration at LPS concentrations well below those effective at increasing neutrophil adherence in vitro. We hypothesized that LPS-induced neutrophil adherence involved a plasma component. In the absence of plasma, high concentrations of LPS (10 micrograms/ml) were required to increase human neutrophil adherence to endothelial cells in vitro. With the inclusion of as little as 1% plasma or serum, however, the LPS dose-response curve was markedly shifted, resulting in increments in adherence at 10 ng/ml, and the time course of enhanced adherence was accelerated. Pretreatment studies suggested that the effect of LPS was on the neutrophil rather than the endothelial cell. Immunoprecipitation of 0111:B4 LPS paralleled the loss of functional activity, suggesting that LPS was an integral part of the active complex, rather than altering a plasma component to make it active. The incubation of plasma with LPS decreased the apparent molecular mass of LPS from 500-1,000 kD to approximately 100 kD. The disaggregated 0111:B4 LPS eluted in the range of albumin and was able to increase adherence in the absence of additional plasma. Plasma depleted of lipoproteins or heat treated retained activity, suggesting that the interaction of LPS with HDL or complement did not account for the observed findings. An LPS-binding protein isolated from rabbit serum enhanced the adherence-inducing effects of both 0111:B4 and Re595 LPS. Furthermore, the activity of rabbit serum was abolished after incubation with an antibody directed against this LPS-binding protein (LBP). An antibody directed against CD14, the putative receptor of the LPS-LBP complex, prevented the adhesive response to LPS. These data suggest that LPS is disaggregated by an LBP in serum and plasma to form an active LPS-plasma component complex. This putative complex then interacts with CD14 on the neutrophil so as to induce an adhesive state.
内毒素血症导致中性粒细胞在多个微循环床中定位，这部分反映了中性粒细胞与血管内皮细胞之间的黏附相互作用。在先前的研究中，用内毒素或脂多糖（LPS）处理兔子，在LPS浓度远低于体外有效增加中性粒细胞黏附的浓度时，就会导致中性粒细胞滞留。我们推测LPS诱导的中性粒细胞黏附涉及血浆成分。在没有血浆的情况下，体外需要高浓度的LPS（10微克/毫升）才能增加人中性粒细胞与内皮细胞的黏附。然而，只要加入低至1%的血浆或血清，LPS剂量反应曲线就会明显偏移，导致在10纳克/毫升时黏附增加，并且增强黏附的时间进程加快。预处理研究表明，LPS的作用是针对中性粒细胞而非内皮细胞。0111:B4 LPS的免疫沉淀与功能活性丧失平行，表明LPS是活性复合物的一个组成部分，而不是改变血浆成分使其具有活性。血浆与LPS孵育会使LPS的表观分子量从500 - 1000 kD降至约100 kD。解聚的0111:B4 LPS在白蛋白范围内洗脱，并且在没有额外血浆的情况下能够增加黏附。去除脂蛋白或经过热处理的血浆仍保留活性，这表明LPS与高密度脂蛋白或补体的相互作用并不能解释观察到的结果。从兔血清中分离出的一种LPS结合蛋白增强了0111:B4和Re595 LPS的诱导黏附作用。此外，兔血清与针对这种LPS结合蛋白（LBP）的抗体孵育后活性被消除。针对LPS - LBP复合物假定受体CD14的抗体可阻止对LPS的黏附反应。这些数据表明，LPS在血清和血浆中被LBP解聚，形成活性LPS - 血浆成分复合物。然后这种假定的复合物与中性粒细胞上的CD14相互作用，从而诱导黏附状态。
