Lee E H, Rikihisa Y
Molecular, Cellular and Developmental Biology Program, The Ohio State University, Columbus 43210, USA.
Infect Immun. 1996 Oct;64(10):4211-9. doi: 10.1128/iai.64.10.4211-4219.1996.
Ehrlichia chaffeensis is a recently isolated minute gram-negative obligatory intracellular bacterium of monocytes/macrophages and is the etiologic agent of human monocytic ehrlichiosis. It is not known how macrophages respond when they encounter ehrlichiae in terms of cytokine production. In this study, we examined cytokine mRNA expression by incubating E. chaffeensis with THP-1 cells and performing competitive reverse transcription-PCR (RT-PCR). At 2 h postinfection, the levels of interleukin-1beta (IL-1beta), IL-8, and IL-10 mRNAs were significant but lower than those following Escherichia coli lipopolysaccharide (LPS) stimulation. Unlike the situation with E. coli LPS stimulation, however, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor alpha (TNF-alpha) mRNAs were not induced. Time course and dose-response studies confirmed the absence of IL-6, GM-CSF, and TNF-alpha mRNA induction with E. chaffeensis. Viable E. chaffeensis organisms were not required for IL-1beta IO, IL-8, and IL-10 mRNA induction, since heat-killed E. chaffeensis induced identical time course responses. IL-1beta, IL-8, and IL-10 mRNAs were detected for up to 21, 21, and 24 h postexposure with E. chaffeensis, respectively, which were shut off more rapidly than with LPS stimulation. Although heat treatment of E. chaffeensis had no effect, periodate treatment completely abolished the ability of E. chaffeensis to induce IL-1beta, IL-8, and IL-10 mRNAs. The capture enzyme-linked immunosorbent assay result corresponded with the RT-PCR results, showing that viable and heat-killed E. chaffeensis produced and secreted the same levels of IL-1beta and IL-8. IL-10 production was significantly reduced by heat treatment. Periodate-treated ehrlichiae did not induce production of any of the cytokines tested. Anti-CD14 monoclonal antibody and polymyxin B did not inhibit IL-1beta mRNA expression upon exposure to E. chaffeensis. The absence of TNF-alpha, IL-6, and GM-CSF mRNA induction may delay the development of a protective immune response, thereby allowing E. chaffeensis to set up residence in macrophages.
恰菲埃立克体是一种最近分离出的微小革兰氏阴性专性细胞内单核细胞/巨噬细胞细菌，是人类单核细胞埃立克体病的病原体。尚不清楚巨噬细胞在遇到埃立克体时细胞因子产生方面的反应情况。在本研究中，我们通过将恰菲埃立克体与THP-1细胞共孵育并进行竞争性逆转录-PCR（RT-PCR）来检测细胞因子mRNA表达。感染后2小时，白细胞介素-1β（IL-1β）、IL-8和IL-10 mRNA水平显著但低于大肠杆菌脂多糖（LPS）刺激后的水平。然而，与大肠杆菌LPS刺激的情况不同，IL-6、粒细胞-巨噬细胞集落刺激因子（GM-CSF）和肿瘤坏死因子α（TNF-α）mRNA未被诱导。时间进程和剂量反应研究证实恰菲埃立克体不会诱导IL-6、GM-CSF和TNF-α mRNA。IL-1β、IL-8和IL-10 mRNA诱导不需要活的恰菲埃立克体生物体，因为热灭活的恰菲埃立克体诱导相同的时间进程反应。分别在与恰菲埃立克体接触后21、21和24小时检测到IL-1β、IL-8和IL-10 mRNA，其关闭速度比LPS刺激更快。尽管对恰菲埃立克体进行热处理没有影响，但高碘酸盐处理完全消除了恰菲埃立克体诱导IL-1β、IL-8和IL-10 mRNA的能力。捕获酶联免疫吸附测定结果与RT-PCR结果一致，表明活的和热灭活的恰菲埃立克体产生和分泌相同水平的IL-1β和IL-8。热处理显著降低了IL-10的产生。高碘酸盐处理的埃立克体未诱导任何测试细胞因子的产生。抗CD14单克隆抗体和多粘菌素B在接触恰菲埃立克体时不抑制IL-1β mRNA表达。TNF-α、IL-6和GM-CSF mRNA未被诱导可能会延迟保护性免疫反应的发展，从而使恰菲埃立克体在巨噬细胞中定居。
