Consequences of chronic Interferon-gamma expression on the host

我们正在利用慢性干扰素-γ表达的小鼠模型来确定对宿主的生物学后果以及这种表型与人类疾病的相关性。我们使用生物信息学的方法来确定干扰素-伽马基因3‘端非翻译部分的保守区。人们认为，这些保守的区域代表了基因结构中的重要调控元件，因为除非mRNA的非编码区提供了一些进化优势，否则不存在通过进化来进行保守的内在原因。基于这一分析，我们针对小鼠干扰素-γ3‘非翻译区的160bp区域进行缺失，因为该区域含有丰富的AUUA序列，并且这些区域先前已被证明在调节细胞因子基因mRNA的不稳定性方面具有重要作用。基因敲除(KO)小鼠已经成功地建立在C57BL/6的遗传背景上，我们的数据表明，与野生型小鼠相比，该小鼠在基础水平和刺激下产生的干扰素-γ显著更多。此外，淋巴结、脾和胸腺的结构被破坏，肝脏显示出慢性炎症的迹象。T细胞动态平衡被破坏，因为存在增加的CD4+和CD8+T细胞，并且小鼠体内的T细胞具有更强的抑制活性。对抗原刺激的TH1反应也增加，而TH2反应降低。B细胞群也会发生变化，基线抗体的产生也会发生偏差。B细胞也在胸腺中以更高的频率被观察到，因此表明干扰素-γ可能改变B细胞的运输。除了表型后果外，B细胞对抗原的反应也被破坏，因为IgM和Ig2aab反应增加，而IgG1反应减少。同时观察到较强的抗DNA和抗核抗原抗体反应，提示慢性干扰素-γ的表达可能在狼疮的发生发展中起一定作用。雌性小鼠还会患上原发性胆管炎，这是一种病因不明的疾病。这是第一个在性别偏见方面概括人类疾病的小鼠模型，因为90%的人类病例是在女性身上。奇怪的是，在Balb/c小鼠中没有看到狼疮样和PBC症状，那里的160个碱基缺失也被交叉到这个遗传背景上。这些小鼠的脾大小增加，淋巴细胞向淋巴结的运输存在明显缺陷。这导致了一种与再生障碍性贫血非常相似的表型。这些效应似乎是干扰素-伽马抑制造血祖细胞在这种小鼠品系中的直接结果。此外，缺失的Balb/c小鼠似乎对肾癌系Renca的挑战更具抵抗力。综上所述，我们对阐明干扰素-γ生物学中涉及的多种机制的方法表明了干扰素-γ基因表达改变宿主内环境平衡的复杂性。除了这些影响，我们现在已经观察到慢性干扰素-g的表达影响小鼠的行为和心脏功能。因此，我们现在已经建立了一个小鼠模型，用于了解和阐明长期慢性干扰素-γ基因表达的系统生物学效应，从而导致宿主的慢性炎症。

We are utilizing a mouse model of chronic IFN-gamma expression to determine the biological consequences to the host and the relevance of this phenotype to human disease. We have used a bioinformatics approach to identify conserved regions of the 3' untranslated portion of the interferon-gamma mRNA. It is believed that these conserved regions represent important regulatory elements in the gene structure, as there would be no inherent reason for conservation through evolution unless the non-coding regions of the mRNA provided some evolutionary advantage. Based on this analysis, we targeted a 160-bp region of the murine interferon-gamma 3' untranslated region for deletion as this region is rich in AUUA sequences, and such regions have been previously shown to be important in the regulation of cytokine gene mRNA instability. The knockout (KO) mouse has been successfully created on the C57 BL/6 genetic background and our data indicates that this mouse produces significantly more interferon-gamma at a basal level and upon stimulation as compared to the wild-type mouse. Furthermore, the architecture of lymph nodes, spleen, and thymus is disrupted and the liver exhibits signs of chronic inflammation. T cell homeostasis has been disrupted as increased CD4+ and CD8+ T cells are present and the T reg cells in the mouse have more potent suppressor activity. There is also an increased TH1 response and a decreased TH2 response to antigenic stimulation. The B cell population is also altered and baseline antibody production is skewed. B cells are also observed in the thymus at increased frequency, thus indicating that IFN-gamma may alter B cell trafficking. In addition to the phenotypic consequences, the B cell response to antigen is also disrupted as increased IgM and Ig2a ab responses are seen with a decrease in the IgG1 response. Strong anti-DNA and anti-nuclear antigen antibody responses are also observed suggesting that chronic IFN-gamma expression may play a role in the development of lupus. The female mice also develop primary biliary cholangitis, a disease that has no known etiology. This is the first mouse model to recapitulate the human disease with respect to sex bias as 90% of the human cases are in women. Curiously, lupus-like and PBC symptoms are not seen in the Balb/c mouse, where the 160-bp deletion has also been crossed onto that genetic background. These mice have increased spleen sizes and an apparent defect in lymphocyte trafficking to the lymph nodes. This results in a phenotype very similar to aplastic anemia. These effects appear to be a direct consequence of interferon-gamma inhibition of hematopoietic progenitors in this mouse strain. In addition, the Balb/c mice with the deletion appear to be more resistant to challenge with the renal carcinoma line RENCA. In summary, our approach towards elucidating the multiple mechanisms involved in the biology of interferon-gamma demonstrates the complexity by which interferon-gamma gene expression alters host homeostasis. In addeition to these effects, we have now observed that chronic IFN-g expression affects mouse behavior and heart function. Thus, we now have developed a mouse model for understanding and elucidating the systems biology effects of long term chronic IFN-gamma gene expression, resulting in chronic inflammation in the host.