Plasmacytoid dendritic cells (pDCs) constitute a unique population of bone marrow-derived cells that play a pivotal role in linking innate and adaptive immune responses. While peripheral tissues are typically devoid of pDCs during steady state, few tissues do host resident pDCs. In the current study, we aim to assess presence and distribution of pDCs in naïve murine limbus and bulbar conjunctiva. Immunofluorescence staining followed by confocal microscopy revealed that the naïve bulbar conjunctiva of wild-type mice hosts CD45⁺ CD11c^low PDCA-1⁺ pDCs. Flow cytometry confirmed the presence of resident pDCs in the bulbar conjunctiva through multiple additional markers, and showed that they express maturation markers, the T cell co-inhibitory molecules PD-L1 and B7–H3, and minor to negligible levels of T cell co-stimulatory molecules CD40, CD86, and ICAM-1. Epi-fluorescent microscopy of DPE-GFP×RAG1^−/− transgenic mice with GFP-tagged pDCs indicated lower density of pDCs in the bulbar conjunctiva compared to the limbus. Further, intravital multiphoton microscopy revealed that resident pDCs accompany the limbal vessels and patrol the intravascular space. In vitro multiphoton microscopy showed that pDCs are attracted to human umbilical vein endothelial cells and interact with them during tube formation. In conclusion, our study shows that the limbus and bulbar conjunctiva are endowed with resident pDCs during steady state, which express maturation and classic T cell co-inhibitory molecules, engulf limbal vessels, and patrol intravascular spaces.

浆细胞样树突状细胞（pDC）构成了一组独特的骨髓源性细胞，它们在连接先天性和适应性免疫反应中起关键作用。虽然外围组织在稳定状态下通常没有pDC，但很少有组织容纳驻留的pDC。在当前的研究中，我们旨在评估幼稚的小鼠角膜缘和延髓结膜中pDC的存在和分布。免疫荧光染色和共聚焦显微镜检查显示，野生型小鼠的初生球结膜具有CD45 ⁺ CD11c^低PDCA-1 ⁺pDC。流式细胞仪通过多种其他标志物证实了结膜结膜中存在驻留的pDC，并表明它们表达成熟标志物，T细胞共抑制分子PD-L1和B7-H3，以及轻微至可忽略的T细胞共-刺激分子CD40，CD86和ICAM-1。具有GFP标签的pDC的DPE-GFP×RAG1 ^-/-转基因小鼠的落射荧光显微镜显示，与角膜缘相比，延髓结膜中pDC的密度较低。此外，活体多光子显微镜检查显示，驻留的pDC伴随着角膜缘血管并在血管内空间巡逻。体外多光子显微镜显示，pDC被吸引到人脐静脉内皮细胞，并在管形成过程中与它们相互作用。总之，我们的研究表明，在稳定状态下，角膜缘和延髓结膜具有常驻pDC，它们表达成熟和经典的T细胞共抑制分子，吞噬角膜血管和在血管内巡逻。