α-Acaridial [2(E)-(4-methyl-3-pentenyl)butenedial] is a novel monoterpene secreted from the house dust mites. Because of its molecular nature of a highly reactive, small lipidic compound, we addressed whether α-acaridial might function as a haptenic allergen that induced allergic contact dermatitis. Mice sensitized with α-acaridial were challenged by the same antigen on the ear skin. After 2 days, significant ear swelling with a prominent infiltration of CD4+ T lymphocytes was observed. In vitro, α-acaridial exhibited an outstanding ability to quickly interact with and chemically modify a reference protein. Virtually all cysteine residues and a sizable fraction of lysine residues were found to be selectively modified, suggesting that α-acaridial could potentially interact with any proteins. Previously, numerous mite-derived proteinaceous allergens have been associated with contact dermatitis. Our study now emphasizes that small lipidic compounds released from mites comprise a new class of mite allergens, and therefore, is of significant medical implications.

• Toshio Sasai(Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Japan)
• Yunosuke Hirano(Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Japan)
• Sayaka Maeda(Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Japan)
• Isamu Matsunaga(Institute for Virus Research, Kyoto University, Japan)
• Atsushi Otsuka(Institute for Virus Research, Kyoto University, Japan)
• Daisuke Morita(Institute for Virus Research, Kyoto University, Japan)
• Ritsuo Nishida(Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Japan)
• Hideo Nakayama(Nakayama Dermatology Clinic, Japan)
• Yasumasa Kuwahara(Department of Bioenvironmental Science, Kyoto Gakuen University, Japan)
• Masahiko Sugita(Institute for Virus Research, Kyoto University, Japan)
• Naoki Mori(Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Japan)