Schlesinger L S, Kaufman T M, Iyer S, Hull S R, Marchiando L K
Department of Medicine, Department of Veterans Affairs Medical Center, University of Iowa, Iowa City 52242, USA.
J Immunol. 1996 Nov 15;157(10):4568-75.
Phagocytosis of the virulent Erdman and H37Rv strains of Mycobacterium tuberculosis, but not that of the attenuated H37Ra strain, by human macrophages is mediated by the mannose receptor (MR) in addition to complement receptors. We have recently determined that a major capsular lipoglycan, lipoarabinomannan (LAM), from the Erdman strain serves as a ligand for the MR during phagocytosis of bacteria. In this study we directly compare uptake of Erdman, H37Rv, and H37Ra LAM by human macrophages and assess the relative contribution of the MR in this process. Microspheres coated with LAM served as model phagocytic particles for studies of LAM as a capsular ligand. Uptake (37 degrees C) of LAM microspheres by monocyte-derived macrophages was greatest for Erdman LAM and intermediate for H37Rv and H37Ra LAM compared with that of buffer microspheres or microspheres coated with LAM from a nontuberculosis strain of mycobacterium (AraLAM). Inhibition of microsphere uptake in the presence of mannan or mannose-BSA was highest for Erdman LAM (75 +/- 8 and 50 +/- 7%, respectively) and H37Rv LAM (57 +/- 13 and 21 +/- 5%, respectively) relative to H37Ra LAM (36 +/- 16 and 22 +/- 11 %, respectively). Inhibition of microsphere uptake in the presence of anti-MR Ab followed a similar pattern: Erdman LAM (80 +/- 9%) > H37Rv LAM (53 +/- 1%) > H37Ra LAM (26 +/- 12%). Attachment (4 degrees C) of microspheres coated with Erdman LAM, H37Rv LAM, and H37Ra LAM was enhanced 12-, 5-, and 4-fold, respectively, compared with that of microspheres coated with AraLAM, and mannose-BSA inhibited attachment of these microspheres by 82 +/- 7, 69 +/- 8, and 12 +/- 17%. Galactose-BSA did not inhibit attachment of any LAM microsphere groups. Chromatographic analyses of mild acid hydrolysates of LAM from Erdman, H37Rv, and H37Ra all revealed the major terminal dimannosyl units. These studies demonstrate differences in the ability of LAM from different M. tuberculosis strains to mediate adherence to macrophages and to serve as ligands for the macrophage MR despite the presence of terminal dimannosyl units. Thus, these studies point toward other subtle structural alterations in LAM among strains that influence initial interactions with human phagocytes.
人巨噬细胞对结核分枝杆菌的强毒株埃尔德曼（Erdman）和H37Rv菌株的吞噬作用，而非对减毒株H37Ra菌株的吞噬作用，除补体受体外还由甘露糖受体（MR）介导。我们最近确定，来自埃尔德曼菌株的一种主要荚膜脂多糖，脂阿拉伯甘露聚糖（LAM），在细菌吞噬过程中作为MR的配体。在本研究中，我们直接比较人巨噬细胞对埃尔德曼、H37Rv和H37Ra LAM的摄取，并评估MR在此过程中的相对贡献。包被LAM的微球用作模型吞噬颗粒，用于研究LAM作为荚膜配体的情况。与缓冲液微球或包被来自非结核分枝杆菌菌株的LAM（阿拉伯糖LAM）的微球相比，单核细胞衍生的巨噬细胞在37℃对埃尔德曼LAM微球的摄取最大，对H37Rv和H37Ra LAM微球的摄取居中。相对于H37Ra LAM（分别为36±16%和22±11%），在甘露聚糖或甘露糖 - 牛血清白蛋白存在下，埃尔德曼LAM（分别为75±8%和50±7%）和H37Rv LAM（分别为57±13%和21±5%）的微球摄取抑制率最高。在抗MR抗体存在下微球摄取的抑制遵循类似模式：埃尔德曼LAM（80±9%）>H37Rv LAM（53±1%）>H37Ra LAM（26±12%）。与包被阿拉伯糖LAM的微球相比，包被埃尔德曼LAM、H37Rv LAM和H37Ra LAM的微球在4℃的附着分别增强了12倍、5倍和4倍，并且甘露糖 - 牛血清白蛋白分别抑制这些微球的附着82±7%、69±8%和12±17%。半乳糖 - 牛血清白蛋白不抑制任何LAM微球组的附着。对埃尔德曼、H37Rv和H37Ra的LAM温和酸水解产物的色谱分析均揭示了主要的末端二甘露糖基单元。这些研究表明，尽管存在末端二甘露糖基单元，但来自不同结核分枝杆菌菌株的LAM介导与巨噬细胞黏附以及作为巨噬细胞MR配体的能力存在差异。因此，这些研究指出了不同菌株LAM中其他细微的结构改变，这些改变影响了与人类吞噬细胞的初始相互作用。
