Roach T I, Barton C H, Chatterjee D, Blackwell J M
Department of Medicine, University of Cambridge Clinical School, U.K.
J Immunol. 1993 Mar 1;150(5):1886-96.
Lipoarabinomannan (LAM) is a major cell-wall associated glycolipid produced by Mycobacterium tuberculosis and Mycobacterium leprae. Previous work demonstrated that LAM from avirulent (H37Ra) and virulent (Erdman) strains of M. tuberculosis differ in structure at their non-reducing termini. In this study the effects of the H37Ra and Erdman LAM on the activation of murine bone marrow-derived macrophages has been investigated. Their abilities to elicit immediate early gene responses at mRNA (c-fos, JE, KC) and protein (TNF-alpha secretion) levels, and nitrite production, was examined. H37Ra LAM, but not Erdman LAM, elicited TNF-alpha secretion at 1000 ng/ml. Neither stimulated production of reactive nitrogen intermediates (RNI). Addition of 25 U/ml IFN-gamma enhanced TNF-alpha secretion in response to H37Ra LAM, reducing the threshold level of LAM required to 10 to 100 ng/ml. In contrast, Erdman LAM at concentrations up to 1000 ng/ml could not induce macrophage TNF-alpha secretion even in the presence of 25 U/ml IFN-gamma. H37Ra LAM also synergized with IFN-gamma to stimulate enhanced production of RNI, whereas IFN-gamma and Erdman LAM did not elicit RNI production. Examination of events before TNF-alpha and RNI production revealed that H37Ra LAM, like LPS, was able to induce increased levels of mRNA expression for c-fos, KC, and JE, with similar kinetics but reduced potency compared with LPS. Erdman LAM in concentrations up to 2500 ng/ml was unable to stimulate c-fos, KC, or JE expression. IFN-gamma at 25 U/ml was itself a potent stimulus of JE expression, and synergized with 1000 ng/ml H37Ra, and to a lesser extent, Erdman LAM for the induction of JE. In contrast, IFN-gamma inhibited H37Ra LAM stimulation of KC expression. The phenomenon of avoiding the stimulation of macrophage immediate early gene expression may be an important determinant of mycobacterial virulence.
脂阿拉伯甘露聚糖（LAM）是结核分枝杆菌和麻风分枝杆菌产生的一种主要的与细胞壁相关的糖脂。先前的研究表明，来自结核分枝杆菌无毒株（H37Ra）和有毒株（埃尔德曼）的LAM在其非还原末端的结构上存在差异。在本研究中，已对H37Ra和埃尔德曼LAM对小鼠骨髓来源巨噬细胞激活的影响进行了研究。检测了它们在mRNA（c-fos、JE、KC）和蛋白质（TNF-α分泌）水平引发即时早期基因反应以及亚硝酸盐产生的能力。H37Ra LAM（而非埃尔德曼LAM）在1000 ng/ml时可引发TNF-α分泌。两者均未刺激活性氮中间体（RNI）的产生。添加25 U/ml的干扰素-γ可增强对H37Ra LAM的TNF-α分泌反应，将所需的LAM阈值水平降低至10至100 ng/ml。相比之下，即使存在25 U/ml的干扰素-γ，浓度高达1000 ng/ml的埃尔德曼LAM也无法诱导巨噬细胞TNF-α分泌。H37Ra LAM还与干扰素-γ协同作用，刺激RNI产生增加，而干扰素-γ和埃尔德曼LAM则未引发RNI产生。对TNF-α和RNI产生之前的事件进行检测发现，H37Ra LAM与脂多糖（LPS）一样，能够诱导c-fos、KC和JE的mRNA表达水平升高，其动力学相似，但效力低于LPS。浓度高达2500 ng/ml的埃尔德曼LAM无法刺激c-fos、KC或JE表达。25 U/ml的干扰素-γ本身是JE表达的有效刺激物，并与1000 ng/ml的H37Ra协同作用，在较小程度上与埃尔德曼LAM协同作用以诱导JE。相比之下，干扰素-γ抑制H37Ra LAM对KC表达的刺激。避免刺激巨噬细胞即时早期基因表达的现象可能是分枝杆菌毒力的一个重要决定因素。
