Role Of Cytokines In The Developing Immune System

已经表明，SIDS可能是由微生物产物和/或其他环境因素（例如环境烟草烟雾（ETS））的组合引起的病理生理反应，此时发育中的免疫系统更容易受到炎症介质的影响。我们已经开发了一种动物模型来模拟双重感染，使用非致死性甲型流感病毒株和亚致死剂量的内毒素。在该模型中，在10日龄接种流感病毒，然后在流感病毒后2天接种内毒素0.2 mg/kg，导致死亡率最低。这些元素成为模型的定义参数。仅当满足特定标准（如感染性损伤之间的时间和幼仔的发育年龄）时才会发生死亡，并且年龄是模型中的关键风险因素。我们已经确定了人类婴儿SIDS病理学的相似性，并在该模型中观察到，并检查了与双重攻击相关的基本免疫因素。这些研究表明，发育中的免疫系统可能会对第二次免疫挑战产生过度反应，导致意外死亡。为了检查导致这种死亡的机制，进行了一系列实验以评估内毒素施用后2-8小时的免疫参数。由于病理结果提示系统性免疫调节而非肺特异性损伤，我们评估了与系统性休克和氧化应激相关的细胞因子反应。在双重激发的幼仔中观察到血清和脾脏IFN γ水平的显著变化，以及脾脏和肺中特异性免疫细胞群的变化。炎症细胞因子基因表达在肺和肝双重攻击的动物达到峰值较早。由于一氧化氮是对细菌和病毒感染的免疫应答的重要方面，因此在靶组织中检测一氧化氮合酶mRNA表达。与仅接受内毒素的动物相比，在双重攻击的动物的肝脏（iNOS、eNOS和nNOS）和肺（iNOS、eNOS）中观察到基因表达增加。我们还研究了内毒素鼻内给药是否会显示类似的免疫学变化模式，内毒素鼻内给药更接近于模拟潜在的人体暴露。在以这种方式激发的动物中未观察到死亡。NIEHS将不再进行进一步的研究;然而，Blood-Siegfried博士将在杜克大学继续这项工作，使用该模型调查环境烟草烟雾在SIDS中的作用。 新生儿暴露于环境污染物2，3，7，8-四氯二苯并对二恶英（TCDD）已被证明会改变胸腺细胞的成熟，并显着损害成年动物的免疫功能。我们假设，产前暴露于TCDD可能会增加或加剧出生后的自身免疫性疾病的遗传倾向MRL/lpr小鼠的发展。我们已经观察到显着的，剂量依赖性增加抗ssDNA，尿蛋白，和肾脏异常TCDD暴露的女性MRL/lpr小鼠相比，在6，10，12周龄，分别。在8周、10周和12周大时接触TCDD的雄性中也观察到类似的结果。

It has been suggested that SIDS may be a patho-physiological response elicited by combinations of microbial products and/or other environmental factors such as environmental tobacco smoke (ETS) at a time when the developing immune system is more vulnerable to the effects of inflammatory mediators. We have developed an animal model to mimic dual infection, using a non-lethal strain of Influenza A virus and a sub-lethal dose of endotoxin. In this model inoculation with influenza at 10 days of age followed by endotoxin 0.2 mg/kg 2 days post influenza caused mortality with the lowest morbidity. These elements became the defining parameters of the model. Mortality only occurred when specific criteria such as timing between infectious insults and developmental age of the pup were met and age was a key risk factor in the model. We have defined similarities of SIDS pathology in human infants and that seen in this model and examined basic immune factors associated with dual challenge. These studies suggest that the developing immune system can be primed to respond in an exaggerated way to a second immune challenge resulting in unexpected death. To examine the mechanisms underlying this mortality, a series of experiments were conducted to evaluate immune parameters 2-8 hours following endotoxin administration. As the pathologic findings a suggested modulation of systemic immunity rather than lung-specific damage, we evaluated cytokine responses related to systemic shock and oxidative stress. Significant alterations in serum and spleen IFN gamma levels were observed in dually challenged pups, as well as changes in specific immune cell populations in the spleen and lung. Inflammatory cytokine gene expression peaked earlier in dually challenged animals in both the lung and liver. As nitric oxide is an important aspect of the immune response to both bacterial and viral infection, nitric oxide synthase mRNA expression was examined in the target tissues. Increased gene expression was observed in the liver (iNOS, eNOS and nNOS) and the lung (iNOS, eNOS) in dually challenged animals as compared to animal receiving only endotoxin. We also investigated whether intranasal administration of endotoxin, which would more closely mimic potential human exposure, would show similar patterns of immunologic changes. No mortality was observed in animals challenged in this fashion. No further studies will be conducted at NIEHS; however, Dr. Blood-Siegfried will continue this work at Duke University investigating the role of environmental tobacco smoke in SIDS using this model. Neonatal exposure to the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been shown to alter thymocyte maturation and significantly impair immune function in adult animals. We hypothesized that prenatal exposure to TCDD may increase or exacerbate post-natal development of autoimmune disease in genetically-prone MRL/lpr mice. We have observed significant, dose-dependent increases in anti-ssDNA, urinary protein, and renal abnormalities in TCDD-exposed female MRL/lpr mice as compared to controls at six, ten, and 12 weeks of age, respectively. Similar results were noted in TCDD-exposed males at eight, ten and 12 weeks of age.