Immunology Letters 134 (2010) 7–16 Contents lists available at ScienceDirect Immunology Letters journal homepage: www.elsevier.com/locate/ 1,25-Dihydroxyvitamin D 3 and all-trans retinoic acid synergistically inhibit the differentiation and expansion of Th17 cells Utako Ikeda a , Daiko Wakita b , Takayuki Ohkuri a , Kenji Chamoto a , Hidemitsu Kitamura a , Yoichiro Iwakura c , Takashi Nishimura a,b,∗ a Division of Immunoregulation, Section of Disease Control, Institute for Genetic Medicine, Hokkaido University, Japan b Division of ROYCE’ Health Bioscience, Section of Disease Control, Institute for Genetic Medicine, Hokkaido University, Japan c Center for Experimental Medicine, Institute of Medical Science, University of Tokyo, Japan article info Article history: Received 7 May 2010 Received in revised form 22 June 2010 Accepted 18 July 2010 Available online 23 July 2010 Keywords: Vitamin D Vitamin A Th17 abstract 1,25-Dihydroxyvitamin D 3 (1,25D3), the active form of vitamin D 3 , is an immunoregulatory hormone with beneficial effects on Th1 cell-mediated inflammatory diseases. Although IL-17-producing CD4 + T helper (Th17) cells have been recently identified as novel effector cells, the immunomodulating effects of 1,25D3 on Th17 cells have not been well defined. We confirmed here that 1,25D3 inhibited the generation of Th17 cells in vitro. Interestingly, 1,25D3 synergistically suppressed the generation of Th17 cells by the combination with all-trans retinoic acid (ATRA). 1,25D3 and ATRA suppressed the development of allergen-induced contact hypersensitivity (CHS) in a mouse ear swelling model. In addition, we found that 1,25D3 and ATRA significantly inhibited the development of human Th17 cells from both naïve and memory human CD4 + T cells. 1,25D3 and ATRA effectively suppressed mRNA expressions of IL-1R1, IL- 21R, IL-23R, RORC, and AHR in human T cells. ATRA further suppressed IL-6R, whereas 1,25D3 did not. Finally, we found that 1,25D3 and ATRA remarkably blocked IL-22 as well as IL-17 mRNA expression in human memory CD4 + T cells. Thus, we initially reveal that 1,25D3 and ATRA have synergistic effects on the generation of Th17 cells, suggesting that the combination with ATRA would provide a promising novel therapy for Th17 cell-related immune diseases including skin inflammation. © 2010 Elsevier B.V. All rights reserved. 1. Introduction It has been well accepted that CD4 + T helper (Th) cells play a pivotal role for the regulation of the immune responses. More than 20 years ago, Mosmann and Coffman [1] defined two distinct CD4 + T cell subsets (Th1 and Th2 cells) in terms of their differential cytokine-producing patterns. Th1 cells, producing IL-2, IFN- and TNF- (type-1 cytokines), have been thought to mediate protective immunity to infectious diseases and tumors [2–5] by promoting effector functions of macrophages, dendritic cells (DCs), natural killer (NK) cells and cytotoxic T lymphocytes (CTLs). However, it is also well known that abnormal activation of Th1 cells promotes pathogenic inflammatory responses [6] and mediates autoimmune Abbreviations: 1,25D3, 1,25-dihydroxyvitamin D3; Ct, comparative Ct; AHR, aryl hydrocarbon receptor; APCs, antigen presenting cells; ATRA, all-trans retinoic acid; CHS, contact hypersensitivity; DNFB, 2,4-dinitrofluorobenzene; PBMCs, peripheral blood mononuclear cells; PMA, phorbol 12-myristate 13-acetate; RAR, retinoic acid receptor; RXR, retinoid X receptor; VDR, vitamin D receptor. ∗ Corresponding author at: Division of Immunoregulation, Section of Disease Con- trol, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan. Tel.: +81 11 706 5519; fax: +81 11 706 5519. E-mail address: tak24@igm.hokudai.ac.jp (T. Nishimura). diseases, such as multiple sclerosis and rheumatoid arthritis [7,8]. On the other hand, Th2 cells, producing IL-4, IL-5, IL-6, IL-10 and IL-13 (type-2 cytokines), have been thought to support the mat- uration of B cells to plasma cells which produce antibodies, and mediate protective immunity to extracellular pathogens although their excessive activation causes allergic diseases [9,10]. Therefore, the proper regulation of the Th1/Th2 balance is required for the maintenance of good health. A seco-steroid hormone, 1,25-dihydroxyvitamin D 3 (1,25D3) is the active form of vitamin D 3 and plays a critical role in the main- tenance of mineral homeostasis and normal skeletal architecture. Moreover, it acts as a potent biological response modifier includ- ing immunomodulatory activities [11]. In relation to the Th1/Th2 balance, 1,25D3 and its derivatives show their immunomodulating activities through their direct effect on naïve CD4 + T cells [12,13] and their indirect effect on DCs [12–14]. It has also been demon- strated that the administration of 1,25D3 prevented Th1-mediated autoimmune diseases in animal models [15–18]. 1,25D3 and its analog also enhance CD4 + CD25 + regulatory T cells in the model of type 1 diabetes [19] and contact hypersensitivity response [20]. In addition, IL-10-producing regulatory T cells can be induced in vitro by 1,25D3 in the presence of dexamethasone [21]. 1,25D3 also represses IL-2 transcriptional activation by direct inhibition 0165-2478/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.imlet.2010.07.002