Abstract: Duan Zhimin, Du Leilei, Liu Caixia, Zeng Rong, Shen Yongnian, Hu Suquan, Liu Weida, Chen Qing, Li Min Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Jiangsu Key Laboratory of Molecular Biology for Skin Diseases and STIs, Nanjing 210042, China （Duan ZM, Li M）; Central Laboratory, Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing 210042, China （Du LL）; Laser Department, Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing 210042, China （Zeng R）; Department of Mycology, Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing 210042, China （Liu CX, Shen YN, Hu SQ, Liu WD）; Research Laboratory, Jiangsu Province Blood Center, Nanjing 210042, China （Chen Q） Corresponding authors: Li Min, Email: drlimin@sina.cn; Chen Qing, Email: qngchen@hotmail.com 【Abstract】 Objective To investigate the roles of Dectin-1 in phagocytosis of Candida albicans （C. albicans） by macrophage-like cells derived from a human acute monocytic leukemia cell line THP-1. Methods THP-1 macrophage-like cells served as the target cells, and were transfected with small interfering RNA （siRNA） targeting Dectin-1 to down-regulate the of Dectin-1 receptor （siRNA-Dectin-1 group）. THP-1 macrophage-like cells transfected with nonsense siRNA （siRNA-NC） served as a negative control group. After transfection, the THP-1 macrophage-like cells in the above 2 groups were co-cultured with heat-killed C. albicans separately. And then, fluorescence microscopy was performed to count THP-1 macrophage-like cells phagocytosing C. albicans, and flow cytometry was used to determine the mean fluorescence intensity （MFI） of dihydrorhodamine （DHR）-123 fluorescent cells. Statistical analysis was done by one-way analysis of variance （ANOVA） and t test with the SPSS19.0 software. Results After transfection with siRNA-Dectin-1, the mRNA and protein of Dectin-1 significantly decreased in THP-1 macrophage-like cells （t = 26.163, P < 0.001）. After 1-, 2-, 4-hour co-culture of THP-1 macrophage-like cells with C. albicans, fluorescence microscopy showed that the phagocytosis rates of C. albicans by THP-1 macrophage-like cells were significantly lower in the siRNA-Dectin-1 group than in the negative control group （17.5% vs. 22.1%, 18.6% vs. 24.3%, 39.2% vs. 59.1%, respectively, all P < 0.05）, so were the percentage of THP-1 macrophage-like cells phagocytosing more than 3 C. albicans cells （2.2% vs. 4.7%, 2.5% vs. 5.4%, 5.1% vs. 8.3%, respectively, all P < 0.05）. After 30-minute, 1-, 2- and 4-hour co-culture of THP-1 macrophage-like cells with DHR-123-labelled C. albicans, flow cytometry showed that the MFI of C. albicans-phagocytosing cells was significantly lower in the siRNA-Dectin-1 group than in the negative control group （36.8 vs. 45.7, 54.3 vs. 62.4, 72.1 vs. 84.9, 93.6 vs. 116.7, respectively, all P < 0.05）. Conclusion Dectin-1 receptor plays an important role in the phagocytosis of C. albicans by macrophages.

Key words: Candida albicans, Macrophages, Phagocytosis, Leukemia, monocytic, acute, Dectin-1