T-cell recruitment to skin tissues is essential for inflammation in different cutaneous diseases; however, the mechanisms by which these T cells access the skin remain unclear. High endothelial venules expressing peripheral node address in (PNAd), an L-selectin ligand, are located in secondary lymphoid organs and are responsible for increasing T-cell influx into the lymphoid tissues. They are also found in non-lymphoid tissues during inflammation. However, their presence in different common inflammatory cutaneous diseases and their correlation with T-cell infiltration remains unclear. Herein, we explored the mechanisms underlying the access of T cells to the skin by investigating the presence of PNAd-expressing vessels in different cutaneous diseases, and its correlation with T cells presence. Skin sections of 43 patients with different diseases were subjected to immunohistochemical and immunofluorescence staining to examine the presence of PNAd-expressing vessels in the dermis. The correlation of the percentage of these vessels in the dermis of these patients with the severity/grade of CD3+ T-cell infiltration was assessed. PNAd-expressing vessels were commonly found in the skin of patients with different inflammatory diseases. A high percentage of these vessels in the dermis was associated with increased severity of CD3+ T-cell infiltration (P < 0.05). Additionally, CD3+ T cells were found both around the PNAd-expressing vessels and within the vessel lumen. PNAd-expressing vessels in cutaneous inflammatory diseases, characterized by CD3+ T-cell infiltration, could be a crucial entry point for T cells into the skin. Thus, selective targeting of these vessels could be beneficial in cutaneous inflammatory disease treatment.

中文翻译：

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PNAd 表达血管是 CD3+ T 细胞介导的皮肤疾病真皮的特征

T 细胞募集到皮肤组织对于不同皮肤疾病的炎症至关重要；然而，这些 T 细胞进入皮肤的机制仍不清楚。高内皮小静脉 (PNAd)（一种 L-选择素配体）表达外周节点地址，位于次级淋巴器官中，负责增加 T 细胞流入淋巴组织。它们也存在于炎症期间的非淋巴组织中。然而，它们在不同常见炎症性皮肤病中的存在及其与 T 细胞浸润的相关性仍不清楚。在此，我们通过研究不同皮肤疾病中 PNAd 表达血管的存在及其与 T 细胞存在的相关性，探讨了 T 细胞进入皮肤的机制。对43例不同疾病患者的皮肤切片进行免疫组织化学和免疫荧光染色，检查真皮中表达PNAd的血管的存在。评估了这些患者真皮中这些血管的百分比与 CD3+ T 细胞浸润的严重程度/等级的相关性。表达 PNAd 的血管常见于患有不同炎症性疾病的患者的皮肤中。真皮中这些血管的高百分比与CD3+T细胞浸润的严重程度增加相关(P＜0.05)。此外，在表达 PNAd 的血管周围和血管腔内都发现了 CD3+ T 细胞。皮肤炎症性疾病中表达 PNAd 的血管以 CD3+ T 细胞浸润为特征，可能是 T 细胞进入皮肤的关键入口点。因此，选择性靶向这些血管可能有益于皮肤炎症性疾病的治疗。