Regulation of Immune Responses to Mycobacterium tuberculosis Infection

摘要 结核病(TB)的疾病结局和病理学是由启动的免疫反应的类型驱动的 然而，在宿主中，免疫细胞成功控制结核病的分子要求仍然很低。 明白了。特别是，尽管IL-10的产生在活动性结核病患者中上调，并已知 拮抗对控制结核分枝杆菌(Mtb)感染至关重要的途径， IL-10在结核分枝杆菌感染中的影响和功能仍然难以捉摸，因为功能研究(即，在 I10-/-小鼠)只产生了最小的表型。我们之前证明了转录因子Bhlhe40 调节多发性硬化症小鼠模型T细胞中IL-10的表达。通过分析已出版的几本书 基因表达数据集，我们现在已经发现BHLHE40转录本的存在明显低于 活动性肺结核患者与健康对照组和潜伏期肺结核患者的比较。这一发现 活动性肺结核患者BHLHE40表达降低导致我们研究其在结核分枝杆菌感染中的作用 在老鼠身上。我们发现，在结核分枝杆菌感染过程中，小鼠失去Bhlhe40会导致IL10的高表达， 细菌负荷较高，对感染的早期易感性。Bhlhe40-/-中观察到的严重表型 小鼠与缺乏STAT1或NF-κB p50的小鼠相似，这两种转录因子都是转录因子 是免疫调节的核心。然而，与STAT1和NF-κB不同的是，Bhlhe40在感染过程中的作用是 完全未知。通过一系列详细的机理研究，我们发现Bhlhe40需要 在结核分枝杆菌感染过程中直接抑制T细胞和CD11c+细胞中IL10的表达，并在 Bhlhe40-/-小鼠逆转了这些小鼠的易感性。我们的初步数据使我们的中央 假设Bhlhe40在结核分枝杆菌感染过程中是基因表达的关键转录调节因子 这是有效控制结核分枝杆菌复制所必需的。我们将通过解剖来开始解决这个假设 Bhlhe40调节IL-10产生的机制以及这如何影响对结核分枝杆菌的敏感性。我们的 研究首次调查了Bhlhe40在感染性疾病和髓系细胞中的作用，并将 提供对感染免疫的分子要求的基本见解。此外, 对Bhlhe40的调查提供了一个独特的机会，可以阐明不同水平的IL-10如何 对结核病的影响，这一点在其他研究中并不明显。检验我们的假设并改进 我们在这些方面的理解，我们将解决以下独立目标：(1)确定如何损失 Bhlhe40在T细胞和CD11c+细胞中对结核分枝杆菌免疫应答的影响，(2)机制剖析 由此Bhlhe40调节免疫细胞中IL10的表达，以及(3)定义 在IL10高表达的情况下对结核分枝杆菌感染的易感性负责。

SUMMARY The disease outcome and pathology of tuberculosis (TB) are driven by the type of immune response mounted in the host, yet the molecular requirements for successful control of TB by immune cells remain poorly understood. In particular, although IL-10 production is upregulated in patients with active TB and is known to antagonize pathways that are essential for the control of Mycobacterium tuberculosis (Mtb) infection, the impact and function of IL-10 during Mtb infection has remained elusive because loss of function studies (i.e, in Il10-/- mice) have yielded only minimal phenotypes. We previously showed that the transcription factor Bhlhe40 regulates IL-10 expression in T cells in a mouse model of multiple sclerosis. By analyzing several published gene expression datasets, we have now found that BHLHE40 transcripts are present in significantly lower abundance in patients with active TB as compared to healthy controls and patients with latent TB. This finding of decreased BHLHE40 expression in patients with active TB led us to investigate its role during Mtb infection in mice. We discovered that loss of Bhlhe40 in mice during Mtb infection results in higher Il10 expression, higher bacterial burden, and early susceptibility to infection. The severe phenotypes observed in Bhlhe40-/- mice are similar to those observed in mice lacking STAT1 or NF-κB p50, both of which are transcription factors central to immune regulation. However, unlike STAT1 and NF-κB, a role for Bhlhe40 during infection is completely unknown. Through a series of detailed mechanistic studies, we find that Bhlhe40 is required to directly repress Il10 expression in T cells and CD11c+ cells during Mtb infection, and deletion of Il10 in Bhlhe40-/- mice reverses the susceptibility of these mice. Our preliminary data have led to our central hypothesis that Bhlhe40 functions as a key transcriptional regulator of gene expression during Mtb infection that is required for effective control of Mtb replication. We will begin to address this hypothesis by dissecting the mechanism by which Bhlhe40 regulates IL-10 production and how this impacts susceptibility to Mtb. Our studies are the first to investigate a role for Bhlhe40 in both infectious disease and in myeloid cells, and will provide fundamental insights into the molecular requirements for immunity to infection. In addition, investigations into Bhlhe40 provide a unique opportunity to shed light on how different levels of IL-10 can impact TB disease, something that has not been evident in other studies. To test our hypothesis and improve our understanding in these areas, we will address the following independent aims: (1) Identify how loss of Bhlhe40 in T cells and CD11c+ cells impacts on immune responses to Mtb, (2) Dissect the mechanism whereby Bhlhe40 regulates Il10 expression in immune cells, and (3) Define the immune responses that are responsible for susceptibility to Mtb infection in the presence of higher Il10 expression.