重视眼表居留免疫细胞群的复杂性

Pay more attentions to the complexity of the resident immune cells in ocular surface

眼表是内眼组织和外部环境之间的特殊界面,它提供了有效的物理和生物屏障以防止环境中的有害物质和病原微生物侵入到眼内.这种保护作用是由眼表独特的解剖结构和细胞成分所决定的,特别是局部居留的免疫细胞,如先天淋巴样细胞（ILCs）、巨噬细胞、肥大细胞、朗格汉斯细胞（LCs）和γδ T细胞.最近的研究强调了LCs和肥大细胞作为免疫耐受诱导细胞的重要性.大多数成人组织的巨噬细胞群体在出生前就已种植到各种组织并保持在稳定状态,而不依赖于来自血液单核细胞的补充.然而,在炎性状态下,单核细胞会瞬时进入到组织成为部分巨噬细胞.单核细胞可以细分为2个主要的表型和功能不同的亚群,一个亚群主要负责对内皮细胞完整性的监控,另一个亚群属于经典的单核细胞,如快速迁移到损伤部位来填补外周组织的树突状细胞和巨噬细胞.此外,在眼表组织中已发现有最新鉴定的ILCs.这些细胞通过产生不同的细胞因子和生长因子来抵御来自外部的不同刺激.累积的数据强调了局部居留的免疫细胞在眼表的自稳态和病理学中发挥着关键性的作用.

Ocular surface is a special interface between the inner ocular tissue and the external environment.It provides effective physical and biological barriers to prevent environmentally harmful substances and pathogenic microbes invading into the eye.This protection is afforded by unique local anatomy and cellular components, especially the resident immune cells such as innate lymphoid cells （ILCs）, macrophages, mast cells, Langerhans cells（LCs） and γδ T cells.Recent studies reinforce the importance of LCs and mast cells as inducers of immune tolerance.Most adult tissue macrophage populations are seeded before birth and maintained in the steady state independently of monocytes from blood.However, under inflammatory condition, some transient monocytes enter into tissue and become macrophage compartments.Monocytes are subdivided into two main phenotypically and functionally distinct subsets.The first main subset is dedicated to the surveillance of endothelial integrity.The second main subset compasses classical monocyte functions such as rapid migration to the sites of injury and the replenishment of peripheral dendritic cells and macrophage compartments.In addition, newly identified ILCs are founded in the ocular surface tissues.These cell groups defens the different stimulus from external environment by producing different cytokines and growth factors.Accumulating data highlight some key roles of tissue-resident immune cells in ocular surface homeostasis and pathology.