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，如风湿性关节炎（RA）或系统性红斑狼疮（SLE）， 这是一个巨大的经济负担，也是一个巨大的负担。由于许多个体对用本发明的药物治疗是难治的， 虽然现有药物的治疗效果不佳，但对于开发用于这些患者的新疗法存在很大的未满足需求。虽然我们知道 B细胞、抗体（Ab）分泌细胞（ASCs）、炎性细胞因子和TLR配体都发挥重要作用， 尽管我们在驱动对病原体、疫苗和自身抗原的体液免疫应答中发挥着重要作用，但我们仍然缺乏一个基本的 了解细胞因子和TLR配体提供的信号如何通过应答B细胞整合， 促进ASCs的发展和扩张，在自身免疫的情况下，ASCs可产生致病性 autoAbs.我们描述了一种不寻常的B细胞亚群（DN 2细胞），这种细胞存在于健康供体（HD）中。 在部分SLE和RA患者中扩增。我们发现，与疾病严重程度相关的DN 2细胞 在SLE中，可以迅速分化为ASC，表明这些细胞是“稳定的”前ASC。我们的数据表明 IFNg提供的早期信号控制SLE患者和HD中DN 2的发展。此外，离体 使用SLE患者DN 2细胞的实验揭示了这些IFNg-“致敏的”前ASC的分化需要 我们观察到由TLR 7配体和IL-21提供的额外信号， 控制人B细胞的TLR 7依赖性而非TLR 9依赖性分化。我们证明了IFNg，但没有 IFN α诱导人B细胞中转录因子IRF 1的表达，IRF 1促进TLR 7驱动的 人ASC形成。因此，我们确定了至少2种，可能3种，独立的B细胞分化 这些途径差异依赖于IFN、IFN诱导的转录因子和TLR配体。至今没有 研究集中在IFNg如何调节B细胞分化以及为什么B细胞响应于IFNg而分化。 TLR 7和TLR 9对IFNg的依赖性不同。在这个提议中，我们将检验我们的中心假设， IFNg选择性诱导B细胞的IRF 1依赖性重编程，从而允许这些细胞分化 对参与TLR 7信号网络的（自身）抗原作出反应。这项建议的近期目标是 （i）检查IFNg和IFNa在促进TLR 7依赖性免疫应答中发挥的重叠和不同的作用， 人ASC发育;（ii）确定IRF 1如何支持B细胞分化和（iii）评估TLR 7- 介导的B细胞分化依赖于IFN衍生的信号。我们的长期目标是利用我们所学到的 控制TLR和苦参碱诱导的B细胞分化的基本机制，以确定干预措施 可以调节健康和疾病中ASCs的形成，维持或功能。本研究是 重要的是，因为我们将首次定义IFN依赖性TLR 7驱动的 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本 了解控制人类B细胞分化的机制，并可能在未来允许选择性地 靶向TLR 7驱动的自身抗体应答而不影响B细胞对其它类型抗原的应答。 !

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. !