Microglial cells are the scions of foetal macrophages which invade the neural tube early during embryogenesis. The nervous tissue environment instigates the phenotypic metamorphosis of foetal macrophages into idiosyncratic surveilling microglia, which are generally characterised by a small cell body and highly ramified motile processes that constantly scan the nervous tissue for signs of changes in homeostasis and allow microglia to perform crucial homeostatic functions. The surveilling microglial phenotype is evolutionarily conserved from early invertebrates to humans. Despite this evolutionary conservation, microglia show substantial heterogeneity in their gene and protein expression, as well as morphological appearance. These differences are age, region and context specific and reflect a high degree of plasticity underlying the life-long adaptation of microglia, supporting the exceptional adaptive capacity of the central nervous system. Microgliocytes are essential elements of cellular network formation and refinement in the developing nervous tissue. Several distinct patrolling modes of microglial processes contribute to the formation, modification, and pruning of synapses; to the support and protection of neurones through microglial–somatic junctions; and to the control of neuronal and axonal excitability by specific microglia–axonal contacts. In pathology, microglia undergo proliferation and reactive remodelling known as microgliosis, which is context dependent, yet represents an evolutionarily conserved defence response. Microgliosis results in the emergence of multiple disease and context-specific reactive states; in addition, neuropathology is associated with the appearance of specific protective or recovery microglial forms. In summary, the plasticity of microglia supports the development and functional activity of healthy nervous tissue and provides highly sophisticated defences against disease.

中文翻译：

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小胶质细胞的可塑性

小胶质细胞是胚胎发生早期侵入神经管的胎儿巨噬细胞的后代。神经组织环境促使胎儿巨噬细胞表型变态为异质的监视小胶质细胞，其通常特征是小细胞体和高度分枝的运动过程，不断扫描神经组织以寻找稳态变化的迹象，并允许小胶质细胞发挥关键的稳态功能. 从早期无脊椎动物到人类，监视小胶质细胞表型在进化上是保守的。尽管存在这种进化保守性，但小胶质细胞在其基因和蛋白质表达以及形态外观方面表现出显着的异质性。这些差异是年龄，特定区域和环境，反映了小胶质细胞终生适应的高度可塑性，支持中枢神经系统的特殊适应能力。小胶质细胞是发育中的神经组织中细胞网络形成和细化的基本要素。小胶质细胞过程的几种不同巡逻模式有助于突触的形成、修饰和修剪；通过小胶质细胞-体细胞连接支持和保护神经元；以及通过特定的小胶质细胞-轴突接触来控制神经元和轴突的兴奋性。在病理学中，小胶质细胞经历了被称为小胶质细胞增生的增殖和反应性重塑，这取决于环境，但代表了一种进化上保守的防御反应。小胶质细胞增生导致多种疾病和特定环境反应状态的出现；此外，神经病理学与特定保护性或恢复性小胶质细胞形式的出现有关。总之，小胶质细胞的可塑性支持健康神经组织的发育和功能活动，并提供高度复杂的疾病防御。