Characterization of PBMC and monocyte subsets in systemic juvenile idiopathic arthritis (sJIA) by single-cell RNA Sequencing: Role of IL-18 and Interferons

系统性幼年特发性关节炎(SJIA)是一种慢性自身炎症性疾病，起病于儿童。患者患有全身性炎症，可进一步发展为危及生命的并发症-巨噬细胞激活综合征(sJIA-MAS)和慢性肺部疾病(sJIA-LD)。这些并发症的定义是先天性免疫细胞激活，导致细胞因子风暴，白细胞介素18(IL-18)和干扰素(干扰素)γ水平显著升高。有趣的是，先前的试点实验表明，通过单细胞RNA测序(scRNA-Seq)观察到活动期sJIA的单核细胞极化发生了变化。为了了解免疫细胞亚群的变化，特别是单核细胞亚群的变化及其在推动IL-18和干扰素过度表达方面的作用，我们的目标是利用单链RNA-序列和建立的流式细胞仪分析板鉴定和表征不同疾病状态下的免疫细胞亚群和转录谱。本项目的进一步目标将集中在接受IL-1β阻断治疗的单纯性焦虑症患者。IL-1β阻滞剂通常用于治疗单纯性脊柱炎患者，至少有40%的患者病情缓解。然而，已有研究发现，IL-1β阻断可上调I型IFN。由于我们先前已经建立了I型β作为sJIA-MAS中IL-18基因表达的驱动因素的要求，这对于IL-1 iFN阻断在sJIA中的应用具有潜在的意义。我们假设，IL-1β阻断通过启动I型干扰素相关途径改变免疫细胞亚群，下游途径可导致IL-18过度表达。因此，我们的目标是用单链RNA序列和流式细胞术来确定sJIA患者在IL-1β阻断前和治疗开始后免疫细胞亚群的变化。一个探索性的目的将是调查细胞表型变化是否与临床反应程度和MAS风险有关。一个特定的焦点将集中在I型干扰素基因和转录途径上，这些途径表征了IL-1、β和IFN之间的关系。拟议的目标将为了解哪些失调的免疫途径驱动sJIA发病机制和危及生命的并发症sJIA-MAS和sJIA-LD，以及免疫细胞如何在sJIA的不同状态下改变其表型以促进疾病进展和IL-18驱动的并发症的发生提供有价值的信息。这些发现可能会导致治疗难治性脊柱炎儿童的新的治疗方法。

Systemic Juvenile Idiopathic Arthritis (sJIA) is a chronic autoinflammatory disease with onset in childhood. Patients suffer from episodes of systemic inflammation, which can further develop into the life-threatening complications macrophage activation syndrome (sJIA-MAS) and chronic lung disease (sJIA-LD). These complications are defined by innate immune cell activation, resulting in a cytokine storm with strongly increased levels of interleukin (IL-) 18 and interferon (IFN)y. Intriguingly, previous pilot experiments suggest a shift of monocyte polarization in active sJIA observed by single cell RNA Sequencing (scRNA-Seq). To understand changes in immune cell and particularly monocyte subpopulations in different sJIA disease states and their contribution to driving IL-18 and IFN overexpression, we aim to identify and characterize immune cell subpopulations and transcriptional profiles in various disease states of sJIA, sJIA-MAS and sJIA-LD and matched healthy controls utilizing scRNA-Seq and an established flow cytometry panel.A further objective of this project will focus on sJIA patients treated with IL-1β blockade. IL-1β blockade is commonly used to treat sJIA patients and results in disease remission in at least 40% of patients. However, it has been found that IL-1β blockade upregulates type I IFNs. As we have previously established a requirement for type I IFNs as driver of IL-18 gene expression in sJIA-MAS, this has potential implications for the application of IL-1β blockade in sJIA. We hypothesize that IL-1β blockade changes immune cell subpopulations by priming type I IFN related pathways that downstream can contribute to IL-18 overexpression. Therefore, we aim to define changes in immune cell subpopulations of sJIA patients using scRNA-Seq and flow cytometry before IL-1β blockade and after treatment initiation. An exploratory aim will be to investigate whether cellular phenotypic changes relate to the degree of clinical response and MAS risk. A specific focus will lie on type I IFN genes and transcriptional pathways that characterize the relationship of IL-1β and IFNs. The proposed objectives will create valuable input for understanding which dysregulated immune pathways drive sJIA pathogenesis and the life-threatening complications sJIA-MAS and sJIA-LD, and how immune cells are shifting their phenotype during different states of sJIA to facilitate disease progression and the onset of complications driven by IL-18. These findings may result in new therapeutic approaches for treatment refractory children with sJIA.