Heumann D, Gallay P, Barras C, Zaech P, Ulevitch R J, Tobias P S, Glauser M P, Baumgartner J D
Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
J Immunol. 1992 Jun 1;148(11):3505-12.
We used flow cytometry to determine how LPS-binding protein (LBP) effects the binding of fluorescein-labeled LPS to human monocytes via receptor-dependent mechanisms. The addition of human, rabbit, mouse, or FCS strikingly increased the binding of LPS to monocytes compared with controls incubated in serum-free medium. This binding was totally prevented by preincubation of monocytes with MY4, an anti-CD14 mAb, or by enzymatic removal of CD14 from monocytes. Depletion of LBP from rabbit serum with anti-LBP antibodies also produced a similar suppression. Solutions of albumin did not support the enhanced binding observed in serum but the addition of purified rabbit LBP to albumin solutions resulted in binding similar to that observed in serum-containing medium. When type-specific anti-LPS mAb was added to human serum, LPS binding to monocytes occurred but was only partly inhibited by anti-CD14 mAb, suggesting that receptors other than CD14 (presumably Fc or complement receptors) were involved. Serum increased by 100- to 1000-fold the sensitivity of monocytes to the triggering by LPS resulting in TNF secretion. TNF secretion was inhibited by anti-CD14 mAb up to 100 ng/ml of LPS and by anti-LPS mAb up to 1 to 10 ng/ml. The inhibition of TNF secretion by anti-LPS mAb appeared to be the result of directing LPS to monocyte receptors other than CD14. In contrast, in medium containing normal as well as acute serum and in the absence of anti-LPS antibodies, the binding of LPS to monocytes and the triggering of TNF secretion appeared to be mediated mainly by interactions between CD14 and LBP-LPS complexes.
我们使用流式细胞术来确定脂多糖结合蛋白（LBP）如何通过受体依赖性机制影响荧光素标记的脂多糖与人单核细胞的结合。与在无血清培养基中孵育的对照相比，添加人、兔、小鼠或胎牛血清显著增加了脂多糖与单核细胞的结合。用抗CD14单克隆抗体MY4对单核细胞进行预孵育，或通过酶法去除单核细胞表面的CD14，可完全阻止这种结合。用抗LBP抗体去除兔血清中的LBP也产生了类似的抑制作用。白蛋白溶液不能支持在血清中观察到的增强结合，但向白蛋白溶液中添加纯化的兔LBP会导致与在含血清培养基中观察到的结合相似的结果。当将型特异性抗脂多糖单克隆抗体添加到人血清中时，脂多糖与单核细胞发生结合，但仅部分被抗CD14单克隆抗体抑制，这表明除CD14外的其他受体（可能是Fc或补体受体）也参与其中。血清使单核细胞对脂多糖触发导致肿瘤坏死因子（TNF）分泌的敏感性提高了100至1000倍。在脂多糖浓度高达100 ng/ml时，抗CD14单克隆抗体可抑制TNF分泌，在脂多糖浓度高达1至10 ng/ml时，抗脂多糖单克隆抗体可抑制TNF分泌。抗脂多糖单克隆抗体对TNF分泌的抑制作用似乎是将脂多糖导向除CD14外的单核细胞受体的结果。相比之下，在含有正常血清以及急性血清且不存在抗脂多糖抗体的培养基中，脂多糖与单核细胞的结合以及TNF分泌的触发似乎主要由CD14与LBP-脂多糖复合物之间的相互作用介导。
