TLR7 and TLR9-directed plasma cell formation: Dissecting the molecular basis for their differential dependence on IFN-induced signals

自身免疫性疾病，如类风湿性关节炎(RA)或系统性红斑狼疮(SLE) 这是一种痛苦，是巨大的财政负担。由于许多人对使用 在现有药物的情况下，为这些患者开发新的治疗方法是一个巨大的未得到满足的需求。尽管我们知道 B细胞、抗体(Ab)分泌细胞(ASCs)、炎症细胞因子和TLR配体都发挥着重要作用 在驱动对病原体、疫苗和自身抗原的体液免疫反应中的作用，我们仍然缺乏基本的 了解细胞因子和TLR配体提供的信号是如何通过反应B细胞来整合的 促进ASCs的发展和扩张，在自身免疫的情况下，ASCs可能会产生致病性 AutoAbs。我们描述了在健康献血者(HD)中发现的一种不寻常的B细胞亚群(DN2细胞)。 并在部分系统性红斑狼疮和类风湿关节炎患者中推广。我们发现，与疾病严重程度相关的DN2细胞 在系统性红斑狼疮中，可以迅速分化为ASCs，这表明这些细胞是ASCs的前身。我们的数据显示 IFNG提供的早期信号控制着SLE患者和HD患者DN2的发展。此外，体外实验 用SLE患者DN2细胞进行的实验表明，这些IFNG“预置”的前ASCs的分化需要 TLR7配体和IL-21提供的其他信号，我们观察到IFNG和IFNA提供的信号 控制依赖于TLR7而不依赖于TLR9的人B细胞分化。我们展示了IFNG，但不是 IFNA诱导人B细胞转录因子IRF1的表达及其促进TLR7的作用 人类ASC队形。因此，我们确定了至少2个，可能是3个独立的B细胞分化 不同的依赖于干扰素、干扰素诱导的转录因子和TLR配体的通路。到目前为止，没有 研究集中在IFNG如何调节B细胞分化，以及为什么B细胞分化反应 TLR7和TLR9对IFNG的依赖程度不同。在这个提案中，我们将检验我们的中心假设 IFNG选择性地诱导依赖IRF1的B细胞重编程，从而允许这些细胞分化 对参与TLR7信号网络的(自动)抗原作出反应。这项建议的直接目标是 是为了(I)审查IFNG和IFNA在促进TLR7依赖方面所发挥的重叠和不同的作用 人类ASC发育；(Ii)确定IRF1如何支持B细胞分化；以及(Iii)评估为什么TLR7- 介导的B细胞分化依赖于干扰素来源的信号。我们的长期目标是利用我们所了解到的 控制TLR和细胞因子诱导B细胞分化的基本机制以确定干预措施 可以调节ASCs的形成、维持或在健康和疾病中的功能。这项研究是 意义重大，因为我们将首次定义依赖于IFNG的TLR7驱动的机制基础 人B细胞分化。我们相信我们的研究是重要的，因为它们将促进我们的基础 了解控制人类B细胞分化的机制，并在未来可能允许选择性地 靶向TLR7驱动的自身抗体反应而不影响B细胞对其他类型抗原的反应。 好了！

Autoimmune disease like Rheumatoid Arthritis (RA) or Systemic Lupus Erythematosus (SLE) cause significant suffering and represent a huge financial burden. Since many individuals are refractory to treatment with the available drugs, there is a large unmet need to develop new therapeutics for these patients. Although we know that B cells, antibody (Ab) secreting cells (ASCs), inflammatory cytokines and TLR ligands all play important roles in driving humoral immune responses to pathogens, vaccines and self-antigens, we still lack a fundamental understanding of how the signals provided by cytokines and TLR ligands are integrated by responding B cells to promote the development and expansion of ASCs, which in the case of autoimmunity may produce pathogenic autoAbs. We characterized an unusual subset of B cells (DN2 cells), which are found in healthy donors (HD) and expanded in some SLE and RA patients. We showed that DN2 cells, which correlate with disease severity in SLE, can rapidly differentiate into ASCs, suggesting that these cells are “poised” pre-ASCs. Our data suggest that early signals provided by IFNg control DN2 development in SLE patients and HD. Moreover, ex vivo experiments using SLE patient DN2 cells reveal that differentiation of these IFNg-“primed” pre-ASCs requires additional signals provided by TLR7 ligands and IL-21 and we observed that signals provided by IFNg and IFNa control TLR7-dependent but not TLR9-dependent differentiation of human B cells. We showed that IFNg but not IFNa induces expression of the transcription factor IRF1 in human B cells and that IRF1 promotes TLR7-driven human ASC formation. Therefore, we identified at least 2, and likely 3, independent B cell differentiation pathways that are differentially reliant on IFNs, IFN-induced transcription factors and TLR ligands. To date, no studies have focused on how IFNg regulates B cell differentiation and why B cell differentiation in response to TLR7 and TLR9 are differentially dependent on IFNg. In this proposal, we will test our central hypothesis that IFNg selectively induces IRF1-dependent reprogramming of B cells, thereby licensing these cells to differentiate in response to (auto)antigens that engage the TLR7 signaling network. The immediate objectives of this proposal are to (i) examine the overlapping and distinct roles that IFNg and IFNa play in promoting TLR7-dependent human ASC development; (ii) determine how IRF1 supports B cell differentiation and (iii) evaluate why TLR7- mediated B cell differentiation is reliant on IFN-derived signals. Our long-term goal is to use what we learn about the fundamental mechanisms controlling TLR and cytokine-induced B cell differentiation to identify interventions that can regulate the formation, maintenance or function of ASCs in health and disease. This research is significant because we will, for the first time, define the mechanistic basis for IFNg-dependent TLR7-driven human B cell differentiation. We believe that our studies are important as they will advance our fundamental understanding of the mechanisms controlling human B cell differentiation and may in the future allow selective targeting of TLR7-driven autoAb responses without affecting B cell responses to other types of antigens. !