Caron E, Peyrard T, Köhler S, Cabane S, Liautard J P, Dornand J
Institut National de la Santé et de la Recherche Médicale U-65, Département Biologie-Santé, Université de Montpellier II, France.
Infect Immun. 1994 Dec;62(12):5267-74. doi: 10.1128/iai.62.12.5267-5274.1994.
Tumor necrosis factor alpha (TNF-alpha) plays a central role in activation of first-line defenses of a host against foreign organisms. To determine whether Brucella infection modulated TNF-alpha production, we measured the biological activity of this cytokine in supernatants of U937 cell-derived macrophages and of fresh human monocytes infected with Brucella spp. Neither the smooth nor rough Brucella strains used induced any measurable TNF-alpha excretion upon infection. On the contrary, as reported before for other gram-negative bacteria, phagocytosis of nonpathogenic Escherichia coli was followed by a rapid and transient induction of TNF-alpha release, suggesting an involvement of this cytokine in some autocrine process. As expected, the Brucella strains tested survived and/or multiplied within U937-derived macrophages, whereas E. coli was rapidly eliminated after phagocytosis. Immunoglobulin G opsonization of E. coli strains enhanced their intracellular killing and strongly potentiated TNF-alpha secretion. Immunoglobulin G opsonization of Brucella strains, in contrast, did not lead to TNF-alpha production, although their rate of intracellular multiplication was reduced. Killed brucellae, however, promoted a significant excretion of TNF-alpha from U937-derived macrophages into cell culture supernatants. We finally demonstrated that pretreatment of U937-derived macrophages with exogenous TNF-alpha significantly inhibited intracellular multiplication of Brucella spp. These results and experiments performed on fresh human monocytes or with isolated lipopolysaccharide (LPS) showed that (i) differences in TNF-alpha production observed during macrophage infection by Brucella spp. and E. coli were not due to differences in LPS structure but resulted from active inhibition of TNF-alpha production by a specific process linked to Brucella spp. and (ii) the capacity of Brucella spp. to use pathways avoiding TNF-alpha production during infection may be considered a major attribute of virulence.
肿瘤坏死因子α（TNF-α）在宿主针对外来生物体的一线防御激活中起核心作用。为了确定布鲁氏菌感染是否调节TNF-α的产生，我们测量了感染布鲁氏菌属的U937细胞衍生巨噬细胞和新鲜人单核细胞培养上清液中这种细胞因子的生物活性。所用的光滑型和粗糙型布鲁氏菌菌株在感染后均未诱导出任何可测量到的TNF-α排泄。相反，正如之前针对其他革兰氏阴性菌所报道的那样，非致病性大肠杆菌被吞噬后会迅速且短暂地诱导TNF-α释放，这表明该细胞因子参与了某些自分泌过程。正如预期的那样，所测试的布鲁氏菌菌株在U937衍生的巨噬细胞内存活和/或增殖，而大肠杆菌在被吞噬后迅速被清除。大肠杆菌菌株的免疫球蛋白G调理作用增强了其细胞内杀伤作用，并强烈增强了TNF-α的分泌。相比之下，布鲁氏菌菌株的免疫球蛋白G调理作用虽然降低了其细胞内增殖速率，但并未导致TNF-α产生。然而，经杀死的布鲁氏菌可促使U937衍生的巨噬细胞向细胞培养上清液中大量排泄TNF-α。我们最终证明，用外源性TNF-α预处理U937衍生的巨噬细胞可显著抑制布鲁氏菌属的细胞内增殖。这些结果以及在新鲜人单核细胞上进行的实验或使用分离的脂多糖（LPS）所做的实验表明：（i）在巨噬细胞被布鲁氏菌属和大肠杆菌感染期间观察到的TNF-α产生差异并非由于LPS结构不同，而是由与布鲁氏菌属相关的特定过程对TNF-α产生的主动抑制所致；（ii）布鲁氏菌属在感染期间利用避免TNF-α产生途径的能力可能被视为一种主要的毒力属性。
