Molecular Immunology 44 (2007) 3222–3233 Microarray analyses in dendritic cells reveal potential biomarkers for chemical-induced skin sensitization Elke Schoeters a,∗ , Geert R. Verheyen a , Inge Nelissen a , An R. Van Rompay a , Jef Hooyberghs a , Rosette L. Van Den Heuvel a , Hilda Witters a , Greet E.R. Schoeters a , Vigor F.I. Van Tendeloo b , Zwi N. Berneman b a Flemish Institute for Technological Research (VITO), Centre of Expertise in Environmental Toxicology, Boeretang 200, 2400 Mol, Belgium b Antwerp University Hospital (UZA), Laboratory of Experimental Hematology, Wilrijkstraat 10, 2650 Edegem, Belgium Received 26 November 2006; accepted 19 January 2007 Available online 19 March 2007 Abstract The assessment of the skin sensitising capacity of chemicals is up to now investigated using in vivo animal tests. However there has been an increasing public and governmental concern regarding the use of animals for chemical screening. This has raised the need for the development of validated in vitro alternatives. Langerhans cells are potent antigen-presenting cells that play a crucial role in the development of allergic contact dermatitis. We used CD34 + progenitor-derived dendritic cells from cord blood as an in vitro alternative for Langerhans cells. The cells were exposed to four contact allergens (nickel sulphate, dinitrochlorobenzene, oxazolone and eugenol) and two irritants (sodium dodecyl sulphate and benzalkonium chloride) for 3, 6, 12 and 24 h. Using microarray analyses we revealed a set of 25 genes with an altered gene expression pattern after exposure to allergens and not to irritants. Five out of these 25 genes were selected and their gene expression changes were confirmed with real-time reverse transcriptase polymerase chain reaction. The list of 25 genes represent valuable candidates to be further evaluated for their capacity to predict the sensitizing potential of different classes of chemicals in studies using a more extended set of (non) allergic substances. © 2007 Elsevier Ltd. All rights reserved. Keywords: Dendritic cells; Sensitization; Microarray 1. Introduction When developing new pharmaceutical or cosmetic products, it is mandatory that the potential of the chemicals used, to cause allergic contact dermatitis can be identified. Up to now, the skin sensitizing potential of chemicals is evaluated using in vivo ani- mal testing methods, e.g. the guinea pig maximalisation test (Magnusson and Kligman, 1969) or the local lymph node assay (Basketter et al., 2002). However, there has been increasing public and governmental concern regarding animal experimen- tation for the screening of chemicals. This has raised the need to Abbreviations: LC, Langerhans cell; DC, dendritic cell; Mo-DC, monocyte- derived DC; CD34-DCCD34 + , progenitor-derived DC; NiSO 4 , nickel sulphate; DNCB, dinitrochlorobenzene; SDS, sodium dodecyl sulphate; RT-PCR, reverse transcriptase polymerase chain reaction; TNF, tumor necrosis factor; PBS, phos- phate buffered saline; FITC, fluorescein isothiocyanate; PE, phycoerythrine ∗ Corresponding author. Tel.: +32 14 33 51 29; fax: +32 14 58 26 57. E-mail address: elke.schoeters@vito.be (E. Schoeters). develop validated in vitro alternative tests to assess the skin sen- sitizing potential of chemicals. In order to develop such a test, it is of great importance to understand the cellular and molecular mechanisms underlying contact allergy. In the first phase of contact allergy, chemical allergens (low molecular weight molecules or haptens) penetrate the skin and come into contact with Langerhans cells (LCs), which belong to the epidermal dendritic cell (DC) family. In order to be taken up by LCs, the hapten needs to bind to a protein. This so-called hapten–protein complex is internalized by LCs, processed and the resulting peptides are presented on their surface, associated with major histocompatibility complex II molecules. During this process, cutaneous cytokines regulate the migration of LCs to the draining lymph nodes and their maturation into immunostimu- latory DCs. In the T cell-rich compartments of the lymph nodes, the mature LCs present the peptides to na¨ ıve T cells which in turn become antigen-specific memory T cells. If in a secondary phase the same allergen is encountered, the circulating memory T cells will be activated and will produce various cytokines 0161-5890/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.molimm.2007.01.031