Supplementary Material for: IL-15 Expression Pattern in Atopic Dermatitis

<b><i>Background:</i></b> An increased expression of interleukin (IL)-15, a cytokine with a key role in stimulating innate and adaptive immune cells, such as dendritic cells (DC), natural killer cells, and T cells, has been observed in infectious and inflammatory diseases, including autoimmune diseases as well as cancer. Atopic dermatitis (AD) is a common inflammatory skin disease characterized by a type 2 immune response. <b><i>Objective:</i></b> To explore the expression of IL-15 and its pattern in AD skin. <b><i>Method:</i></b> Immunofluorescence staining was performed on skin specimens of AD skin, nonlesional AD skin (AD NL), and normal skin (NS) using antibodies directed against IL-15 and CD3, mast cell tryptase, eosinophil cationic protein, CD68, CD11b, CD1a, and vimentin. <b><i>Results:</i></b> A significantly higher IL-15 expression in AD and AD NL was observed in both the epidermis (<i>p</i> = 0.0003) and the dermis (<i>p</i> = 0.0154) as compared to NS. Cells expressing IL-15 were mainly keratinocytes, CD1a⁺ DC, CD11b⁺ DC, CD68⁺ macrophages, and vimentin⁺ fibroblasts. In AD, an increase in the relative numbers of IL-15 expressing CD1a⁺ DC, macrophages, and fibroblasts was noted. <b><i>Conclusion:</i></b> Our results demonstrate an expression of IL-15 in AD similar to that of eosinophilic esophagitis which is also a type 2 disease. IL-15 may serve as a therapeutic target for AD.

**背景：** 白细胞介素-15（interleukin, IL-15）是一种在激活先天与适应性免疫细胞（如树突状细胞（dendritic cell, DC）、自然杀伤细胞及T细胞）中发挥关键作用的细胞因子，在包括自身免疫病、癌症在内的感染性与炎症性疾病中均被观察到表达水平上调。特应性皮炎（atopic dermatitis, AD）是一类以2型免疫应答为特征的常见炎症性皮肤病。**目的：** 本研究旨在探究IL-15在特应性皮炎皮肤中的表达情况及其分布模式。**方法：** 本研究针对特应性皮炎皮损皮肤、特应性皮炎非皮损皮肤（AD NL）与正常皮肤（NS）标本，采用靶向IL-15、CD3、肥大细胞类胰蛋白酶（mast cell tryptase）、嗜酸性粒细胞阳离子蛋白（eosinophil cationic protein）、CD68、CD11b、CD1a及波形蛋白（vimentin）的抗体开展免疫荧光染色。**结果：** 相较于正常皮肤，特应性皮炎皮损皮肤与非皮损皮肤的表皮层（*p* = 0.0003）及真皮层（*p* = 0.0154）中IL-15的表达水平均显著升高。表达IL-15的细胞主要为角质形成细胞、CD1a⁺树突状细胞、CD11b⁺树突状细胞、CD68⁺巨噬细胞及波形蛋白⁺成纤维细胞。在特应性皮炎皮损组织中，表达IL-15的CD1a⁺树突状细胞、巨噬细胞与成纤维细胞的相对数量均有所增加。**结论：** 本研究结果显示，特应性皮炎中IL-15的表达模式与同样属于2型疾病的嗜酸性粒细胞性食管炎（eosinophilic esophagitis）相似。IL-15或可作为特应性皮炎的治疗靶点。