Abstract: Ma Lei *, Xue Haibo, Guan Xiuhao, Shu Chunmei, Yu Juan, Zhang Junhua, Yun Beilei. *Department of Dermatology, Affiliated Hospital of Binzhou Medical University, Binzhou 256603, Shandong, China Corresponding author: Xue Haibo, Email: xuehaibo@sina.com 【Abstract】 Objective To detect the expressions of miR-155, T helper type 17 （Th17） cells, and Th17 cell-specific transcription factor RORγt and effector cytokine interleukin （IL）-17 in peripheral blood and skin lesions from, and to evaluate their relationship in, patients with atopic dermatitis （AD）. Methods Peripheral blood was obtained from 37 patients with AD and 33 age- and sex-matched healthy controls, and biopsy specimens from the lesional and perilesional skin of five patients with severe AD as well as from the normal skin of five healthy human controls. Real-time fluorescence-based reverse transcription （RT）-PCR was employed to measure the mRNA expression levels of miR-155, RORγt and IL-17 in peripheral blood mononuclear cells （PBMCs） and skin specimens, flow cytometry to detect the percentage of Th17 cells in PBMCs, enzyme-linked immunosorbent assay （ELISA） to determine the plasma concentration of IL-17. Statistical analysis was done using independent sample′s t test, one-way analysis of variance followed by the least significant difference test, and linear correlation analysis. Results Compared with the healthy controls, the patients with AD showed a significant increase in Th17 cell percentage（1.78% ± 0.52% vs. 0.47% ± 0.15%, P < 0.01）, mRNA expression levels of miR-155 （5.78 ± 1.78 vs. 1.82 ± 0.46, P < 0.01）, RORγt （6.08 ± 1.04 vs. 1.64 ± 0.52, P < 0.01） and IL-17 （7.09 ± 1.75 vs. 1.71 ± 0.46, P < 0.01）, as well as in the plasma concentration of IL-17 （（2.51 ± 6.15） pg/ml vs. （11.80 ± 2.24） pg/ml, P < 0.01）. There was a sequential decrease in the expression levels of miR-155, RORγt and IL-17 mRNA from lesional skin, perilesional skin to normal skin（F = 41.803, 17.040 and 37.064 respectively, all P < 0.01）. The miR-155 mRNA expression level in PBMCs was positively correlated with the SCORing Atopic Dermatitis （SCORAD） index, Th17 cell percentage, RORγt and IL-17 mRNA expression levels as well as IL-17 plasma concentration （r = 0.405, 0.426, 0.402, 0.410 and 0.408 respectively, all P < 0.05）. Similarly, the miR-155 expression level was positively correlated with RORγt and IL-17 mRNA expression levels in lesional and paralesional specimens （r = 0.428 and 0.435 respectively, both P < 0.05）. Conclusion The up-regulated expression of miR-155, Th17 cells and their effector cytokine IL-17 may be associated with the development of AD.

Key words: Dermatitis, atopic, miR-155, Th17 cells