REGULATION OF CYTOKINE PRODUCTION BY IL-10 IN ENDOTOXIN-STIMULATED MONOCYTES

用细菌内毒素刺激人单核细胞， 脂多糖（LPS），诱导多种细胞因子的表达， 包括肿瘤坏死因子（TNF-a）、白细胞介素-1（IL-1b）、IL-6和 IL-10。 IL-10的表达相对于TNF-α、IL-1b和IL-13的表达延迟。 IL-6。 此外，IL-10反馈抑制TNF-α、IL-1b的表达 和IL-6，从而提供了一种有效的自分泌机制， 单核细胞中的促炎细胞因子产生。 我们发现 Th1型淋巴因子IFN-g显著上调TNF-α的产生 在内毒素刺激的单核细胞中， IFN-γ的产生部分是由于其抑制IL-10的能力 单核细胞中的生产。 核分析表明，这些 作用是转录介导的。 因此，TNF-α的增强 IFN-γ在单核细胞中的产生与内源性 IL-10表达（Donnelly等人，1995. 155：1420 - 1427）。 与IFN-g的作用相反，IL-10下调IFN-γ的产生 单核细胞中的TNF-α。 在未来的实验中，我们将尝试定义 IL-10下调细胞因子产生的机制， TNF-α，在活化的单核细胞中。 在这方面，我们还将审查 通过比较这些IL-10诱导效应的细胞类型特异性， IL-10对纯化的人细胞群中细胞因子产生的影响 单核细胞和T细胞。 在初步实验中，我们发现， 尽管IL-10显著抑制单核细胞中TNF-α的产生， 不抑制活化T细胞中TNF-α的表达。 进一步 明确IFN-γ和IL-10对单核细胞功能活性的作用， 我们正在评估这两种细胞因子对合成的影响， 通过释放TNF受体，特别是II型TNF受体 LPS刺激的单核细胞。 TNF-R从单核细胞脱落， LPS刺激，并可作为TNF拮抗剂，通过竞争 与膜TNF-R（mTNF-R）。 我们已经发现，IFN-g下调 mTNF-RII和可溶性TNF-RII（sTNF-RII）的表达， LPS刺激的单核细胞。 sTNF-RII的产生减少， IFN-γ处理的单核细胞的培养物与降低的 TNF-R Ⅱ mRNA水平与TNF-α mRNA水平呈负相关。 在 相反，IL-10上调sTNF-RII的产生，并显著抑制 生产TNF-a。 IL-10还阻断IFN-g抑制IL-10表达的能力。 sTNF-RII的产生和增强TNF-α的产生。 这些 研究结果表明，IL-10协同下调 TNF-α（一种TNF-受体激动剂），并上调sTNF-RII（a TNF-R拮抗剂）。 IL-10目前正在作为一种 用于治疗许多炎性疾病的潜在治疗剂 疾病，包括类风湿性关节炎和克罗恩病。 的 这些研究的结果将提高我们对生物学的认识。 IL-10的作用，从而提高我们调节 这种生物制剂的临床应用。

Stimulation of human monocytes with bacterial endotoxin, lipopolysaccharide (LPS), induces expression of multiple cytokines, including tumor necrosis factor (TNF-a), interleukin-1 (IL-1b), IL-6 and IL-10. IL-10 expression is delayed relative to that of TNF-a, IL-1b and IL-6. Furthermore, IL-10 feedback inhibits expression of TNF-a, IL-1b and IL-6, thus providing an efficient autocrine mechanism for controlling proinflammatory cytokine production in monocytes. We have found that the Th1-type lymphokine, IFN-g, markedly up-regulates production of TNF-a in endotoxin-stimulated monocytes, and that this potentiation of cytokine production by IFN-g is due in part to its ability to suppress IL-10 production in monocytes. Nuclear run-on analyses showed that these effects are transcriptionally-mediated. Thus, potentiation of TNF-a production by IFN-g in monocytes is coupled to inhibition of endogenous IL-10 expression (Donnelly et al. 1995. J. Immunol. 155:1420-1427). In contrast to the effects of IFN-g, IL-10 down-regulates production of TNF-a in monocytes. In future experiments, we will attempt to define the mechanism by which IL-10 down-regulates cytokine production, particularly TNF-a, in activated monocytes. In this context, we will also examine the cell type specificity of these IL-10-induced effects by comparing the effects of IL-10 on cytokine production in purified populations of human monocytes and T cells. In preliminary experiments, we have found that although IL-10 markedly inhibits production of TNF-a in monocytes, it does not inhibit expression of TNF-a in activated T cells. To further define the actions of IFN-g and IL-10 on monocyte functional activities, we are evaluating the effects of these two cytokines on synthesis and release of TNF receptors, particularly type-II TNF receptors, by LPS-stimulated monocytes. TNF-R are shed from monocytes after stimulation by LPS, and can function as TNF antagonists by competing with membrane TNF-R (mTNF-R). We have found that IFN-g down-regulates expression of both mTNF-RII and solubleTNF-RII (sTNF-RII) by LPS-stimulated monocytes. The decreased production of sTNF-RII in cultures of IFN-g-treated monocytes correlates directly with decreased levels of TNF-RII mRNA and inversely with the levels of TNF-a mRNA. In contrast, IL-10 up-regulates production of sTNF-RII and markedly inhibits production of TNF-a. IL-10 also blocks the ability of IFN-g to suppress production of sTNF-RII and to potentiate production of TNF-a. These findings demonstrate that IL-10 coordinately down-regulates production of TNF-a (a TNF-R agonist), and up-regulates production of sTNF-RII (a TNF-R antagonist) in monocytes. IL-10 is currently being tested as a potential therapeutic agent for the treatment of a number of inflammatory diseases, including rheumatoid arthritis and Chron's disease. The results of these studies will enhance our knowledge of the biological actions of IL-10, and thereby improve our ability to regulate the clinical use of this biologic agent.