Biology of the Eosinophilic Leukocyte

我们实验室项目的主要焦点之一是嗜酸性粒细胞，这是一种神秘的白细胞，其在宿主防御中的作用仍然是一个有重大争议的主题。我们实验室的几项研究使我们考虑嗜酸性粒细胞分泌核糖核酸酶的作用（在项目编号AI 000942 -01中进一步描述），并通过扩展，其主要宿主细胞嗜酸性粒细胞在宿主防御先前未识别的靶病原体组中的作用，特别是副粘病毒科的呼吸道病毒（在项目编号AI 000943 -01中进一步描述）。 作为我们对嗜酸性粒细胞及其在炎症中作用的更大兴趣的一部分，我们已经启动了一项广泛的基因微阵列研究，旨在探索小鼠体内嗜酸性粒细胞的性质和发育。这项工作的结果，题为--基因微阵列分析揭示了小鼠骨髓中白细胞介素-5依赖性转录靶点--于2004年初发表在《血液》杂志上（参考文献3），并通过题为--嗜酸性白细胞中纤溶酶原激活物抑制剂-2（派-2）--（参考文献15）的后续研究得到补充。在第一项研究的最突出的发现中，我们观察到7至40倍增加的转录编码经典嗜酸性粒细胞颗粒蛋白（嗜酸性粒细胞过氧化物酶，主要碱性蛋白，核糖核酸酶）以及花生四烯酸-15-脂氧合酶和蛋白酶抑制剂派-2，在IL-5生产，感染的野生型小鼠。这是伴随着参与分泌蛋白生物合成和颗粒囊泡形成的基因转录增加。有趣的是，我们没有检测到编码嗜酸性粒细胞相关趋化因子受体（CCR 1，CCR 3）或加塔或C/EBP转录因子家族成员的基因表达增加。这些数据表明，小鼠骨髓中的IL-5反应性祖细胞已经显著定型为嗜酸性粒细胞谱系，并且IL-5促进这些定型祖细胞分化为具有可识别和特征性细胞质颗粒和颗粒蛋白的细胞。 在后续研究（参考文献15）中，我们证明了纯化人嗜酸性粒细胞提取物中存在的免疫反应性派-2蛋白的可变浓度范围为30 - 444 ng/10 E6细胞，这是评价的所有白细胞亚型中最高的每细胞浓度。酶法证实，嗜酸性粒细胞来源的派-2是生物活性和抑制其优选的底物，尿激酶（u-PA）的激活，并进一步的研究表明，在特定的颗粒定位。免疫反应性派-2也检测到细胞外沉积物中和周围的嗜酸性粒细胞富集的肉芽肿组织封装的寄生虫卵感染的蠕虫寄生虫，曼氏血吸虫的野生型小鼠的肝脏。我们目前正在探索这种蛋白酶抑制剂在派-2和各种嗜酸性粒细胞耗尽或嗜酸性粒细胞缺乏的基因缺失小鼠品系中的作用。

One of the primary focus projects of our laboratory program centers on the eosinophil, an enigmatic leukocyte whose role in host defense remains a subject of significat controversy. Several lines of investigation from our laboratory have led us to consider the role of the eosinophil secretory ribonucleases (described further in Project Number AI000942-01), and by extension, the role of their primary host cells, the eosinophils, in host defense against a previously unrecognized group of target pathogens, specifically respiratory viruses of the family Paramyxoviridae (described further in Project Number AI000943-01). As part of our larger interest in eosinophils and their role in inflammation, we have initiated an extensive gene microarray study designed to explore the nature and development of mouse eosinophils in vivo. The results of this work, entitled--Gene microarray analysis reveals interleukin-5-dependent transcriptional targets in mouse bone marrow--were published in Blood in early 2004 (ref #3) and were augmented by a followup study entitled--Plasminogen activator inhibitor-2 (PAI-2) in eosinophilic leukocytes--(ref #15). Among the most prominent findings of the first study, we observed 7 to 40-fold increased expression of transcripts encoding the classic eosinophil granule proteins (eosinophil peroxidase, major basic protein, the ribonucleases) together with arachidonate-15-lipoxygenase and protease inhibitor PAI-2, in the IL-5-producing, infected wild type mice only. This was accompanied by increased transcription of genes involved in secretory protein biosynthesis and granule-vesicle formation. Interestingly, we did not detect increased expression of genes encoding eosinophil-related chemokine receptors (CCR1, CCR3) or members of the GATA or C/EBP transcription factor families. These data suggest that the IL-5 responsive progenitors in the mouse bone marrow are already significantly committed to the eosinophil lineage, and that IL-5 promotes differentiation of these committed progenitors into cells with recognizable and characteristic cytoplasmic granules and granule proteins. In the followup study (ref #15), we demonstrated that immunoreactive PAI-2 protein present in extracts of purified human eosinophils at variable concentrations ranging from 30 to 444 ng/10E6 cells, which is the highest per cell concentration among all leukocyte subtypes evaluated. Enzymatic assay confirmed that eosinophil-derived PAI-2 is biologically active and inhibits activation of its preferred substrate, urokinase (u-PA), and further studies demonstrated localization in the specific granules. Immunoreactive PAI-2 was also detected in extracellular deposits in and around the eosinophil-enriched granuloma tissue encapsulating the parasitic egg in livers of wild type mice infected with the helminthic parasite, Schistosoma mansoni. We are currently exploring the role of this protease inhibitor in both PAI-2 and various eosinophil-depleted or eosinophil-devoid strains of gene-deleted mice.