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

细菌内毒素对人单核细胞的刺激作用 脂多糖，诱导多种细胞因子的表达， 包括肿瘤坏死因子(TNF-a)、白介素1(IL-1b)、IL-6和 IL-10。IL-10的表达相对于肿瘤坏死因子-a、IL-1b和 IL-6。IL-10反馈抑制肿瘤坏死因子-a、IL-1b的表达 和IL-6，从而提供了一种有效的自分泌机制 单核细胞产生促炎细胞因子。我们发现， Th1型淋巴因子--干扰素-g显著上调肿瘤坏死因子-a的产生 在内毒素刺激的单核细胞中，这种细胞因子的增强 干扰素-g的产生部分归因于其抑制IL-10的能力 在单核细胞中产生。核运行分析表明，这些 影响是由转录调节的。因此，肿瘤坏死因子-a的增强作用 单核细胞产生干扰素-g与内源性抑制有关 IL-10的表达(Donnelly et al.1995年。J.免疫。155：1420-1427)。 与干扰素-g的作用不同，IL-10下调 单核细胞中的肿瘤坏死因子-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，特别是 活化的单核细胞中的肿瘤坏死因子-α。在这方面，我们还将研究 通过比较IL-10诱导的这些效应的细胞类型特异性 IL-10对人纯种细胞产生细胞因子的影响 单核细胞和T细胞。在初步实验中，我们发现 尽管IL-10显著抑制单核细胞产生肿瘤坏死因子-α，但它 不抑制活化T细胞中肿瘤坏死因子-α的表达。为了进一步 明确干扰素-g和白介素10对单核细胞功能活动的作用， 我们正在评估这两种细胞因子对合成和 释放肿瘤坏死因子受体，特别是II型肿瘤坏死因子受体 内毒素刺激单核细胞。单核细胞分泌肿瘤坏死因子受体 内毒素刺激，并可通过竞争发挥肿瘤坏死因子拮抗剂的作用 与膜上的肿瘤坏死因子受体(mtnf-R)。我们已经发现干扰素-g下调了 Mtnf-RII和可溶性肿瘤坏死因子-RII(sTNF-RII)的表达 内毒素刺激单核细胞。人外周血中sTNF-RII的减少 经干扰素-g处理的单核细胞培养与 TNF-RII基因表达水平与肿瘤坏死因子-α基因表达水平呈负相关。在……里面 相反，IL-10上调sTNF-RII的产生，并明显抑制 产生肿瘤坏死因子-α。IL-10也阻断了干扰素-g抑制的能力 产生sTNF-RII，增强肿瘤坏死因子-α的产生。这些 研究结果表明，IL-10协同下调产量 肿瘤坏死因子受体激动剂，并上调sTNF-RII(a 肿瘤坏死因子受体拮抗剂)。IL-10目前正在作为一种 用于治疗多种炎症性疾病的潜在治疗剂 疾病，包括类风湿性关节炎和慢性疾病。这个 这些研究的结果将提高我们对生物的认识 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.