Abstract: Yu Lu, Wang Hua, Luo Xiaoyan. Department of Dermatology, Children's Hospital, Chongqing Medical University, Chongqing 400014, China Corresponding author: Luo Xiaoyan, Email: luoxycq@hotmail.com 【Abstract】 Objective To determine the proportion of T helper 17（Th17） cells in peripheral blood mononuclear cells （PBMCs） from children with acute atopic dermatitis （AD）, and to evaluate the effect of tacrolimus and Staphylococcus aureus enterotoxin B （SEB） on the proportion. Methods PBMCs were separated from 86 children with moderate to severe acute AD and 81 healthy children, and cultured in the presence of phorbol ester （PMA） and ionomycin with or without tacrolimus or SEB for different durations. Then, flow cytometry was performed to determine the proportions of Th17, Th1 and Th2 cells, enzyme-linked immunosorbent assay （ELISA） to measure the levels of interleukin （IL）-17, interferon （IFN）-γ and IL-4 in the culture supernatant of these cells, and real-time fluorescence-based quantitative PCR（RT-PCR） to detect the expression level of RORγt mRNA. Statistical analysis was done by using two independent samples t-test, chi-square test and analysis of variance. Results After stimulation with PMA and ionomycin, there was a significant increase in the proportions of Th2 and Th17 cells in, supernatant levels of IL-17 and IL-4 and mRNA expression level of RORγt of, but a significant decrease in Th1 cell percentage in and IFN-γ supernatant level of, PBMCs from patients with AD compared with PBMCs from the healthy controls （all P < 0.01）. The combination treatment with tacrolimus significantly reduced the supernatant levels of IL-17, IFN-γ, IL-4 and RORγt mRNA expression level of PBMCs from both the patients and healthy controls compared with those treated with PMA and ionomycin only （all P < 0.01）. In comparison with the healthy controls, the patients with AD showed significantly higher proportions of Th17 and Th2 cells in, supernatant levels of IL-17 and IL-4 of, and expression level of RORγt mRNA of, but significantly lower proportion of Th1 cells in and IFN-γ supernatant level of, PBMCs after SEB treatment （all P < 0.01）. Conclusions Tacrolimus evidently inhibits the secretion of IL-17, IFN-γ and IL-4 by PBMCs from both children with AD and healthy children, while SEB can up-regulate the proportion of peripheral blood Th17 cells in children with AD.

Key words: Dermatitis, atopic, Tacrolimus, Staphylococcus aureus, Enterotoxins, Th17 cells