Macrophage migration inhibitory factor (MIF) is an important regulator of innate immunity with key roles in neural regeneration and responses to pathogens, amongst a multitude of other functions. The expression of MIF and its binding partners has been characterised throughout the nervous system, with one key exception: the primary olfactory nervous system. Here, we showed in young mice (postnatal day 10) that MIF is expressed in the olfactory nerve by olfactory ensheathing glial cells (OECs) and by olfactory nerve fibroblasts. We also examined the expression of potential binding partners for MIF, and found that the serine protease HTRA1, known to be inhibited by MIF, was also expressed at high levels by OECs and olfactory fibroblasts in vivo and in vitro. We also demonstrated that MIF mediated segregation between OECs and J774a.1 cells (a monocyte/macrophage cell line) in co-culture, which suggests that MIF contributes to the fact that macrophages are largely absent from olfactory nerve fascicles. Phagocytosis assays of axonal debris demonstrated that MIF strongly stimulates phagocytosis by OECs, which indicates that MIF may play a role in the response of OECs to the continual turnover of olfactory axons that occurs throughout life.

中文翻译：

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巨噬细胞迁移抑制因子及其结合伴侣HTRA1由嗅鞘细胞表达。

巨噬细胞迁移抑制因子（MIF）是先天免疫的重要调节剂，在众多其他功能中，在神经再生和对病原体的反应中起关键作用。MIF及其结合伴侣的表达已在整个神经系统中得到了表征，但有一个关键的例外：原发性嗅觉神经系统。在这里，我们在幼鼠（出生后第10天）中显示，嗅觉鞘膜神经胶质细胞（OEC）和嗅觉神经成纤维细胞在嗅觉神经中表达MIF。我们还检查了MIF潜在结合伴侣的表达，发现在体内外，OEC和嗅觉成纤维细胞还以高水平表达了已知受MIF抑制的丝氨酸蛋白酶HTRA1。我们还证明了MIF介导了OEC与J774a之间的隔离。共培养物中有1个细胞（单核细胞/巨噬细胞系），这表明MIF有助于嗅觉神经束中巨噬细胞的缺失。轴突碎片的吞噬作用分析表明，MIF强烈刺激OEC吞噬，这表明MIF可能在OEC对一生中发生的嗅轴突持续更新的反应中发挥作用。