The minor house dust mite allergen Der p 13 is a fatty acid-binding protein and an activator of a TLR2-mediated innate immune response DOI: :10.1111/all.12899 Abstract: Background: The house dust mite (HDM) allergen Der p 13 could be a lipid-binding protein able to activate key innate signaling pathways in the initiation of the allergic response. We investigated the IgE reactivity of recombinant Der p 13 (rDer p 13), its lipid-binding activities, and its capacity to stimulate airway epithelium cells. Methods: Purified rDer p 13 was characterized by mass spectrometry, circular dichroism, fluorescence-based lipid-binding assays, and in silico structural prediction. IgE-binding activity and allergenic potential of Der p 13 were examined by ELISA,basophil degranulation assays, and in vitro airway epithelial cell activation assays. Results: Protein modeling and biophysical analysis indicated that Der p 13 adopts a b-barrel structure with a predominately apolar pocket representing a potential binding site for hydrophobic ligands. Fluorescent lipid-binding assays confirmed that the protein is highly selective for ligands and that it binds a fatty acid with a dissociation constant typical of lipid transporter proteins. The low IgE-binding frequency (7%, n = 224) in Thai HDM-allergic patients as well as the limited propensity to activate basophil degranulation classifies Der p 13 as a minor HDM allergen. Nevertheless, the protein with its presumptively associated lipid(s) triggered the production of IL-8 and GM-CSF in respiratory epithelial cells through a TLR2-, MyD88-, NF-kB-, and MAPK-dependent signaling pathway. Conclusions: Although a minor allergen, Der p 13 may, through its lipid-binding capacity, play a role in the initiation of the HDM-allergic response through TLR2 activation. First Author: P. Satitsuksanoa Correspondence: Assoc. Prof. Dr. Alain Jacquet, Department of Medicine, Faculty of Medicine, Chulalongkorn University All Authors: P. Satitsuksanoa, M. Kennedy, D. Gilis, M. Le Mignon, N. Suratannon, W. T. Soh, J. Wongpiyabovorn, P. Chatchatee, M. Vangveravong, T. Rerkpattanapipat, A. Sangasapaviliya, S. Piboonpocanun, E.