Abstract: XING Chen-jing*， LIN Fu-quan, WU Ji-long, FU Li-fang, WANG Sui-quan, OUYANG Jie, XU Ai-e. *Third People′s Hospital of Hanzhou, Hangzhou Clinical College Affiliated to Anhui Medical University, Hangzhou 310009, China Corresponding author: XU Ai-e, Email: xuaiehz@msn.com 【Abstract】 Objective To evaluate the effect of calcipotriol on the proliferation of and cytokine secretion by melanocytes and perilesional CD8+ cytotoxic T lymphocytes （CTLs） from patients with vitiligo. Methods Melanocytes isolated from abdominal skin and CD8+ CTLs from perilesional skin of patients with vitiligo were subjected to successive culture in vitro. After several passages, the melanocytes and CD8+ CTLs were cultured alone or in combination with or without the presence of various concentrations of calcipotriol for 24 to 48 hours. MTS （3-（4,5-dimethylthiazol-2-yl）-5-（3-carboxymethoxyphenyl）-2-（4-sulfopheny）-2H-tetrazolium, inner salt） method was used to evaluate the proliferative activity of cells, enzyme-linked immunosorbent assay to determine the levels of interleukin （IL）-6, tumor necrosis factor （TNF）-α and interferon （IFN）-γ in the culture supernatant of cells, flow cytometry to detect cell apoptosis. Some co-cultured melanocytes and CTLs were treated with calcipotriol of 10－8 mol/L and anti-IL-6 antibody of various concentrations （0, 1, 2, 2.5, 5, 10 mg/L） for two days followed by enumeration of cells. The concentrations of 10－8 and 10－9 mol/L （calcipotriol） were chosen for relevant tests. Results There was a marked apoptosis in MCs after coculture with CD8+ CTLs. The 24-hour treatment with calcipotriol of 10－8 and 10－9 mol/L had no obvious effect on the proliferation of melanocytes cultured alone （both P > 0.05）, but accelerated the proliferation of melanocytes cocultured with CTLs （both P < 0.05） as well as that of CD8+ CTLs cultured alone or in combination with melanocytes （all P < 0.05）. A statistical decrease was observed in IL-6, TNF-α and IFN-γ levels in the supernatant of cocultured melanocytes and CTLs compared with those in the supernatant of melanocytes and CTLs cultured alone, and calcipotriol of 10－9 mol/L intensified the decrease in supernatant IL-6 level （t = 2.89, P < 0.05）, but no statistical changes were noted for the level of TNF-α or IFN-γ in the supernatant of the coculture system after treatment with calcipotriol of 10－8 or 10－9 mol/L compared with that before treatment （both P > 0.05）. In the coculture system pretreated with calcipotriol of 10－8 mol/L, the number of CD8+ CTLs significantly decreased（t = 3.15, P < 0.05）, whereas that of melanocytes significantly increased （t = 3.53, P < 0.05） after the treatment with anti-IL-6 antibody of 5 mg/L. Conclusions Perilesional CD8+ CTLs have a specific cytotoxic effect on melanocytes, and calcipotriol may inhibit the cytotoxic effect of CD8+ CTLs by suppressing the secretion of IL-6, which may partly explain the therapeutic mechanism of calcipotriol for vitiligo. 【Key words】 Melanocytes; T-lymphocytes, cytotoxic; CD8-positive T-lymphocytes; Calcipotriol; Cytokines

Key words: Cytokines