The Role Of Cytokines In The Developing Immune System

我们假设，特定的事件在发展中的免疫系统被改变的环境暴露。上呼吸道感染等损伤可能使新生儿更容易受到后期感染的影响。我们与杜克大学的Jane Blood-Siegfried博士合作，设计了一种上呼吸道感染和细菌性脓毒症双重感染模型，在近交系大鼠中诱导SIDS样病理。使用这个模型，我们已经建立了一个临界窗口的双重感染的侮辱，这将导致一个SIDS样死亡。在流感后两天给予流感和内毒素的新生大鼠幼仔在2 mg/kg、0.5 mg/kg和0.2 mg/kg剂量下内毒素后7-23小时内的死亡率为73%。0.05 mg/kg内毒素组无死亡，流感或仅内毒素对照组无死亡。Abraham Nyska博士（LEP）的评价表明，对照幼仔中无大体病理学发现。在用两种药物激发的动物中，尸检时的特定肉眼和显微镜变化与SIDS婴儿尸检时发现的变化相似。给予0.2 mg/kg内毒素的幼仔肺部出现瘀点和出血、脾脏轻度充血和其他退行性病变，与人SIDS死亡的病理学结果一致。Nyskas博士的评价表明，该模型中的死亡率与全身性事件有关，而不是特定的肺损伤。与仅内毒素或仅RAIV对照组相比，在双重感染大鼠幼仔中观察到血清干扰素γ水平和脾白细胞群的显著差异。在死亡率增加的关键时期，脾脏中巨噬细胞活化增加和自然杀伤细胞数量增加表明TH-1型免疫应答过度。已提交了一份详细说明基线免疫参数和病变病理学的手稿供发表。有充分的证据表明，自身免疫性疾病的易感性在很大程度上取决于特定的主要组织相容性复合体（MHC）基因型的存在，然而，疾病症状的发展似乎也需要关键的环境因素，如细菌或病毒感染或化学暴露。我们正在研究产前和成人暴露于环境因子在自身免疫发展中的作用。虽然发育暴露的影响可能是至关重要的，这些影响还没有得到全面研究，在适当的啮齿动物模型倾向于自身免疫功能障碍。我们已经开始检查出生后的免疫后果产前暴露于内分泌干扰化学品的自身免疫易感啮齿动物。我们研究了MRL/lpr自身免疫易感小鼠在妊娠期间暴露于TCDD的自身免疫性疾病的发病率增加和/或恶化的可能性。MRL/lpr小鼠表现出与在患有系统性红斑狼疮的人类患者中观察到的相似的严重肾坏死（肾小球肾炎），雌性小鼠通常在约14-16周龄时呈现针对核蛋白颗粒的循环自身抗体，随后呈现肾补体-抗体免疫复合物，而雄性小鼠在20-22周龄时呈现。通过定量ssDNA血清自身抗体、尿蛋白水平和肾组织病理学评估的自身免疫严重程度在雌性与雄性小鼠中进行比较，以确定是否存在差异化学诱导效应。雌性小鼠的结果表明，与对照组相比，TCDD暴露动物在6周、10周和12周时的抗ssDNA抗体、尿蛋白和肾脏异常分别呈剂量依赖性显著增加。在8周、10周和12周大时接触二恶英的雄性中也观察到类似的结果。

We hypothesized that specific events in the developing immune system are altered by environmental exposures. Insults such as upper respiratory tract infections could make neonates more susceptible to the effects of later infections. In collaboration with Dr. Jane Blood-Siegfried at Duke University, we have designed a dual infection model of upper respiratory tract infection and bacterial sepsis to induce a SIDS-like pathology in an inbred rat strain. Using this model, we have established a critical window of dual infectious insults, which result in a SIDS-like death. Neonatal rat pups given influenza and endotoxin two days post influenza had a 73% mortality rate within 7-23 hours post endotoxin for doses of 2 mg/kg, 0.5 mg/kg and 0.2 mg/kg. There were no deaths with 0.05 mg/kg endotoxin and no mortality in the influenza or endotoxin only control groups. Evaluation by Dr. Abraham Nyska, LEP indicates that there were no gross pathology findings in the control pups. In animals challenged with both agents, specific gross and microscopic changes on necropsy were similar to those found on autopsy of SIDS infants. Pups dosed with 0.2 mg/kg endotoxin had petechiae and hemorrhage in the lungs, mild congestion of the spleen and other degenerative lesions consistent with the pathological findings in human SIDS deaths. Dr. Nyskas evaluation suggests that mortality in this model is related to a systemic event rather than specific lung damage. Significant differences were observed in serum interferon gamma levels and splenic leukocyte populations in dual-infected rat pups as compared to endotoxin-only or RAIV-only controls. Increased macrophage activation and increased numbers of natural killer cells in the spleen during the critical period for increased mortality suggest an exaggerated TH-1 type immune response. A manuscript detailing the baseline immune parameters and pathology of the lesion has been submitted for publication. It is well documented that autoimmune disease susceptibility is largely dependent upon the presence of particular major histocompatibility complex (MHC) genotypes, however, development of disease symptoms also appears to require critical environmental factors, such as bacterial or viral infections or chemical exposure. We are examining the role of prenatal and adult exposures to environmental agents in the development of autoimmunity. Although the effects of developmental exposure may be of critical importance, these effects have not been comprehensively studied in appropriate rodent models predisposed to autoimmune dysfunction. We have begun to examine postnatal immune consequences of prenatal exposure to endocrine disrupting chemical in autoimmune-prone rodents. We have examined the potential for increased incidence and/or exacerbation of autoimmune disease in MRL/lpr autoimmune-prone mice exposed during gestation to TCDD. MRL/lpr mice exhibit severe renal necrosis (glomerulonephritis) similar to that observed in human patients with systemic lupus erythematosus, with females normally presenting circulating autoantibodies against nucleoprotein particles and subsequent renal complement-antibody immune complexes at approximately 14-16 weeks of age vs. males at 20-22 weeks. Severity of autoimmunity as assessed via quantitation of serum autoantibodies to ssDNA, urinary protein levels, and renal histopathology was compared in female versus male mice to determine if differential chemical-induced effects were present. Results in female mice indicated a significant, dose-dependent increase in anti-ssDNA, urinary protein, and renal abnormalities in TCDD-exposed animals as compared to controls at six, ten, and 12 weeks of age, respectively. Similar results were noted in dioxin-exposed males at eight, ten and 12 weeks of age.