Kim H Y, Rikihisa Y
Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio 43210-1093, USA.
Infect Immun. 2000 Jun;68(6):3394-402. doi: 10.1128/IAI.68.6.3394-3402.2000.
Human granulocytic ehrlichiosis (HGE) is an emerging febrile systemic disease caused by the HGE agent, an obligatory intracellular bacterium of granulocytes. The pathogenicity- and immunity-related mechanisms of HGE are unknown. In this study, several cytokines generated in human peripheral blood leukocytes (PBLs) incubated with the HGE agent or a recombinant 44-kDa major surface protein (rP44) of the HGE agent were examined by reverse transcription-PCR and a capture enzyme-linked immunosorbent assay. The HGE agent induced expression of interleukin-1beta (IL-1beta), tumor necrosis factor alpha (TNF-alpha), and IL-6 mRNAs and proteins in PBLs in a dose-dependent manner to levels as high as those resulting from Escherichia coli lipopolysaccharide stimulation. The kinetics of induction of these three cytokines in PBLs by rP44 and by the HGE agent were similar. Proteinase K treatment of the HGE agent or rP44 eliminated the ability to induce these three cytokines. Induction of these cytokine mRNAs was not dependent on superoxide generation. These results suggest that P44 proteins have a major role in inducing the production of proinflammatory cytokines by PBLs. Expression of IL-8, IL-10, gamma interferon, transforming growth factor beta, and IL-2 mRNAs in response to the HGE agent was not remarkable. Among PBLs, neutrophils and lymphocytes expressed IL-1beta mRNA but not TNF-alpha or IL-6 mRNA in response to the HGE agent, whereas monocytes expressed all three of these cytokine mRNAs. These observations suggest that induction of proinflammatory-cytokine gene expression by the major outer membrane protein of the HGE agent in monocytes, which are not the primary host cells of the HGE agent, contributes to HGE pathogenesis and immunomodulation.
人粒细胞埃立克体病（HGE）是一种由HGE病原体引起的新出现的发热性全身性疾病，HGE病原体是粒细胞的专性细胞内细菌。HGE的致病性和免疫相关机制尚不清楚。在本研究中，通过逆转录-聚合酶链反应和捕获酶联免疫吸附测定法，检测了用HGE病原体或HGE病原体的重组44 kDa主要表面蛋白（rP44）孵育的人外周血白细胞（PBL）中产生的几种细胞因子。HGE病原体以剂量依赖的方式诱导PBL中白细胞介素-1β（IL-1β）、肿瘤坏死因子α（TNF-α）和IL-6 mRNA及蛋白的表达，其水平高达大肠杆菌脂多糖刺激所产生的水平。rP44和HGE病原体在PBL中诱导这三种细胞因子的动力学相似。用蛋白酶K处理HGE病原体或rP44可消除诱导这三种细胞因子的能力。这些细胞因子mRNA的诱导不依赖于超氧化物的产生。这些结果表明，P44蛋白在诱导PBL产生促炎细胞因子中起主要作用。HGE病原体刺激后，IL-8、IL-10、γ干扰素、转化生长因子β和IL-2 mRNA的表达不显著。在PBL中，中性粒细胞和淋巴细胞在受到HGE病原体刺激时表达IL-1β mRNA，但不表达TNF-α或IL-6 mRNA，而单核细胞表达所有这三种细胞因子mRNA。这些观察结果表明，HGE病原体的主要外膜蛋白在单核细胞（而非HGE病原体的主要宿主细胞）中诱导促炎细胞因子基因表达，这有助于HGE的发病机制和免疫调节。
