Abnormal cytokine response and autoantigen production in IgA-producing subpopulations in IgA nephropathy

摘要 伊加肾病（IgAN）是最常见的原发性肾小球肾炎。会导致晚期肾病 （ESKD）40-50%的患者。IgAN患者通常表现出肉眼血尿，通常与 上呼吸道感染这种在粘膜感染发作期间观察到的肾损伤加重 而炎症则表明两者之间存在联系在IgAN患者的活检中， 这种疾病的特征是多聚IgA 1的沉积，通常与IgG和补体C3共沉积。 存款沉积的IgA 1的分析揭示了半乳糖缺陷型IgA 1（Gd-IgA 1）的富集， 循环IgA 1。此外，共沉积的IgG对Gd-IgA 1具有特异性。这似乎是免疫 复杂的沉积，这也是发现在病人的循环。血清Gd-IgA 1和抗Gd-IgA 1抗体水平 IgG自身抗体在IgAN患者中升高，与疾病进展相关，并且可以发现 在循环中复杂。这种循环自身抗原（Gd-IgA 1）通常以聚合物形式存在， 是粘膜区域所特有的。这表明一个产生IgA 1的细胞亚群可能从 粘膜区域，或有异常的IgA 1产生细胞形成的其他地方。初步观察发现， IgAN患者中与一过性血尿相关的感染导致了这样的论点， 刺激可增加循环中含Gd-IgA 1的免疫复合物，引起肾损伤。我们 最近发表了IL-6刺激来自IgAN患者的EBV永生化的产生IgA 1的细胞，但不是 对照组，由于增强和延长的STAT 3激活，优先增加Gd-IgA 1的产生。在 此外，我们实验室的初步数据来自使用永生化IgA产生的单细胞转录组分析， 来自IgAN患者和健康对照的细胞揭示了多种产生IgA 1的细胞群， 对细胞因子刺激的不同反应。这些观察结果导致我们的假设，增强Gd- IgA 1产生是IgA 1产生细胞亚群中异常细胞因子应答的结果。在目标1中， 我们将检验细胞因子暴露对IgA 1产生细胞亚群有不同影响的假设， 来自IgAN患者与健康和疾病对照的EBV永生化的IgA 1产生细胞。在目标2中，我们 检验对细胞因子刺激有不同反应的IgA 1产生细胞亚群的假设， 优先产生Gd-IgA 1。这两个目标的结合将有助于确定特定的IgA 1- 产生有助于自身抗原产生的细胞亚群。这些研究将使测试新的 研究假设，并产生新的初步数据，以形成竞争性的R 01提案。

Abstract IgA nephropathy (IgAN) is the most common primary glomerulonephritis. It leads to end-stage kidney disease (ESKD) in 40-50% of patients. IgAN patients often exhibit macroscopic hematuria, commonly associated with upper-respiratory tract infections. This exacerbation of kidney injury seen during episodes of mucosal infection and inflammation suggests a connection between the two. In biopsies of IgAN patients, the defining characteristic of this disease is the deposits of polymeric IgA1, typically with IgG and complement C3 co- deposits. Analysis of the deposited IgA1 revealed enrichment for galactose-deficient IgA1 (Gd-IgA1) compared to circulatory IgA1. In addition, the co-deposited IgG is specific for Gd-IgA1. This appears to be immune complex deposition, which is also found in circulation of patients. Serum levels of Gd-IgA1 and anti-Gd-IgA1- IgG autoantibodies are elevated in IgAN patients, associate with disease progression, and can be found complexed in circulation. This circulatory autoantigen (Gd-IgA1) is typically found in the polymeric form, which is unique to the mucosal region. This suggests that a subset of IgA1-producing cells could be migrating from mucosal regions, or there is abnormal IgA1-producing cells formed elsewhere. Initial observations that mucosal infections associated with transient hematuria in IgAN patients led to the thesis that pro-inflammatory stimulation could increase circulatory Gd-IgA1-containing immune complexes, causing renal injury. We recently published that IL-6 stimulation in EBV-immortalized IgA1-producing cells from IgAN patients, but not controls, preferentially increased Gd-IgA1 production due to an enhanced and prolonged STAT3 activation. In addition, preliminary data in our lab from single-cell transcriptome profiling using immortalized IgA-producing cells from IgAN patients and healthy controls revealed multiple populations of IgA1-producing cells that have differential responses to cytokine stimulation. These observations led to our hypothesis that enhanced Gd- IgA1 production is a result of abnormal cytokine response in a subset of IgA1-producing cells. In Aim 1, we will test the hypothesis that cytokine exposure has differential effects on subsets of IgA1-producing cells in EBV- immortalized IgA1-producing cells from IgAN patients vs. healthy and disease controls. In Aim 2, we will test the hypothesis that subsets of IgA1-producing cells that have differential responses to cytokine stimulation are preferentially producing Gd-IgA1. The combination of these two aims will help identify the specific IgA1- producing cell subsets that contribute to autoantigen production. These studies will enable testing of novel research hypotheses and yield new preliminary data towards a competitive R01 proposal.