Cytokine Signaling and Primary Immunodeficiency

细胞因子代表大量分泌的蛋白质，调节细胞生长和分化。这些因子在调节免疫和炎症反应以及调节淋巴样细胞的发育和分化方面尤为重要。毫不奇怪，细胞因子在类风湿性关节炎、系统性红斑狼疮、炎症性肠病和牛皮癣等自身免疫性疾病的发病机制中起着关键作用。相反，影响细胞因子和细胞因子信号通路的突变是各种初级免疫缺陷的基础。 我们发现了人类JAK3，一种通过结合共同伽马链的细胞因子GC(IL-2、IL-4、IL-7、IL-9、IL-15和IL-21)进行信号传递所必需的激酶。我们发现JAK3的突变会导致一种称为严重联合免疫缺陷(SCID)的原发性免疫缺陷疾病。我们有一个临床方案，允许我们评估疑似JAK3缺乏症患者。今年没有新的患者入选。 在受体相关的JAK激活后，信号转导的下一步是激活潜伏的胞浆转录因子，这些转录因子也可以结合激活的细胞因子受体。这些因子被称为STATs(信号转导和转录激活剂)。二十年来，STAT蛋白在免疫细胞中的功能一直是这个实验室的重点。NIH科学家最近的工作揭示了另一种原发免疫缺陷综合征，约伯氏综合征或高免疫球蛋白E综合征，是由STAT3突变引起的。基于我们的小鼠研究，我们调查了人类STAT3突变是否与Th17分化受损有关。我们发现，患有约伯氏综合症的患者就是这种情况。STAT3的突变是高IgE综合征(HIEs)的基础，但STAT3在发病机制中的作用一直受到与STAT3胚系缺失相关的致命性的阻碍。此外，导致IgE过度产生的机制尚不清楚。为了更好地了解这种复杂的初级免疫缺陷，我们建立了这种疾病的小鼠模型。我们发现，表达HIEs-STAT3等位基因的转基因小鼠概括了HIEs的一些方面，包括升高的血清IgE。突变的B细胞在体外激活后表现出Ig种系转录和开关重组的增加，表明高IgE缺陷是B细胞固有的。目前，我们正在剖析STAT3在造血细胞和基质细胞中的相对作用。利用这些小鼠，我们正在进行骨髓移植实验。这些结果可能对HIE患者有重要的意义。 我们还采用了新技术，开始在全基因组范围内定义STAT3靶点。具体地说，我们使用染色质免疫沉淀和大规模并行测序来全面枚举Th17细胞中的STAT3靶基因。我们发现STAT3与参与Th17细胞分化、细胞激活、增殖和存活的多个基因结合，调节表达和表观遗传修饰。因此，STAT3在炎症和动态平衡中协调T细胞功能的多个关键方面。

Cytokines represent a large number of secreted proteins that regulate cell growth and differentiation. These factors are especially important in regulating immune and inflammatory responses, and in regulating lymphoid development and differentiation. Not surprisingly, cytokines are critical in the pathogenesis of autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease and psoriasis. Conversely, mutations that affect cytokines and cytokine signal pathways underlie a variety of primary immunodeficiencies. We discovered human Jak3, a kinase essential for signaling by cytokines that bind the common gamma chain, gc (IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21). We found that mutation of Jak3 results in a primary immunodeficiency disorder termed severe combined immunodeficiency (SCID). We have a clinical protocol that allows us to evaluate patients with suspected Jak3 deficiency. No new patients were enrolled this year. After activation of receptor-associated Jaks, the next step in signal transduction is the activation of latent, cytosolic transcription factors that can also bind activated cytokine receptors. These factors are called STATs (signal transducers and activators of transcription). The function of STAT proteins in immune cells has been a focus of this lab for two decades. Recent work by NIH scientists has revealed that another primary immunodeficiency syndrome, Job's or Hyperimmunoglobulin E syndrome, is due to STAT3 mutations. Based on our mouse studies, we investigated whether mutations of STAT3 in humans are associated with impaired Th17 differentiation. We found this to be the case in patients with Job's syndrome. Mutations of STAT3 underlie hyper-IgE syndrome (HIES), but deciphering STAT3s role in pathogenesis has been hampered by the lethality associated with germline deletion of Stat3. Furthermore, the mechanisms responsible for IgE hyperproduction are unknown. To better understand this complicated primary immunodeficiency, we generated a mouse model of the disease. We found that transgenic mice expressing a HIES-Stat3 allele recapitulate aspects of HIES, including elevated serum IgE. Mutant B cells display increased Ig germline transcription and switch recombination upon ex-vivo activation, demonstrating that the hyper-IgE defect is B cell intrinsic. At present, we are dissecting the relative roles of STAT3 in hematopoietic versus stromal cells. Using these mice, we are performing bone marrow transplantation experiments. These results may have important implications for patients with HIES. We have also employed new technology to begin to define STAT3 targets genome-wide. Specifically, we have used chromatin immunoprecipitation and massive parallel sequencing to comprehensively enumerate STAT3 target genes in Th17 cells. We found that STAT3 bound to multiple genes involved in Th17 cell differentiation, cell activation, proliferation, and survival, regulating both expression and epigenetic modifications. Thus, STAT3 orchestrates multiple critical aspects of T cell function in inflammation and homeostasis.