Miyazawa K, Mantel C, Lu L, Morrison D C, Broxmeyer H E
Department of Medicine (Hematology/Oncology), Indiana University School of Medicine, Indianapolis 46202.
J Immunol. 1991 Jan 15;146(2):723-9.
Lactoferrin (LF) has been implicated in a number of functions including the negative regulation of myelopoiesis in vitro and in vivo, an effect mediated by suppression of cytokine release from monocytes/macrophages. This suppression is abrogated by bacterial LPS. In the present study, HL-60 cells were induced to differentiate to monocytes/macrophages by 12-O-tetradecanoyl phorbol-13-acetate, and LF-binding assays were performed. After differentiation, HL-60 cells showed a twofold increase of LF-binding sites with no difference in the specificity or affinity of LF between pre- and post-differentiated cells. CD11a, CD11b, and CD11c Ag, which have been associated with specific binding sites for LPS on monocytes/macrophages, were also increased three- to fourfold after differentiation. With the use of this system, the effect of LPS on LF binding was studied. At 37 degrees C, LPS enhanced LF binding on HL-60 cells, especially after differentiation. Conversely, at 4 degrees C, LPS inhibited LF binding. There was little effect of temperature on LF binding in the absence of LPS. In the presence of polymyxin B sulfate, the enhanced LF binding by LPS was abrogated. Also, pretreatment with mAbCD11 and/or mAb5D3, which are associated with or directed against candidate LPS receptors, reduced LF binding. Cross-linking studies using an iodinated, photoactivatable LPS derivative ([125I]ASD-LPS) demonstrated directly the specific binding of LPS to LF. These data indicate a dichotomous nature of LF binding on monocyte/macrophage-differentiated HL-60 cells--one being mediated by specific LF receptors whereas the other is apparently mainly via LPS receptors after formation of an LF-LPS complex. These interactions, for which a model is proposed, help to explain the mechanism behind LPS abrogation of the myelopoietic suppressive effects of LF, and a situation that probably occurs during bacterial infection.
乳铁蛋白（LF）具有多种功能，包括在体外和体内对骨髓生成的负调控，这种作用是通过抑制单核细胞/巨噬细胞释放细胞因子介导的。细菌脂多糖（LPS）可消除这种抑制作用。在本研究中，用12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯诱导HL - 60细胞分化为单核细胞/巨噬细胞，并进行LF结合试验。分化后，HL - 60细胞的LF结合位点增加了两倍，分化前后细胞之间LF的特异性或亲和力没有差异。与单核细胞/巨噬细胞上LPS特异性结合位点相关的CD11a、CD11b和CD11c抗原在分化后也增加了三到四倍。利用该系统，研究了LPS对LF结合的影响。在37℃时，LPS增强了HL - 60细胞上的LF结合，尤其是在分化后。相反，在4℃时，LPS抑制LF结合。在没有LPS的情况下，温度对LF结合几乎没有影响。在存在硫酸多粘菌素B的情况下，LPS增强的LF结合被消除。此外，用与候选LPS受体相关或针对其的单克隆抗体mAbCD11和/或mAb5D3预处理可降低LF结合。使用碘化的、可光活化的LPS衍生物（[125I]ASD - LPS）进行的交联研究直接证明了LPS与LF的特异性结合。这些数据表明，在单核细胞/巨噬细胞分化的HL - 60细胞上，LF结合具有二分性——一种是由特异性LF受体介导，而另一种显然主要是在形成LF - LPS复合物后通过LPS受体介导。本文提出了一个模型来解释这些相互作用，这有助于解释LPS消除LF骨髓抑制作用背后的机制，以及细菌感染期间可能发生的情况。
