Thermostable. Upon heating, unfolds only partially even at 95 degrees Celsius. Upon cooling to room temperature, almost completely restores its structure, indicating high heat stability and refolding capacity. Monomer (PubMed:24874917). Homodimer (PubMed:18445190). Associated with cytoplasmic matrix, detached cytoplasmatic material and with electron-dense droplets, which presumably represent transport vesicles. Expressed in the epithelium, lumen and microvilli of the midgut, and in feces. Causes an allergic reaction in human. Recombinant protein binds to IgE in patients allergic to house dust mite (HDM) (PubMed:18445190, PubMed:24874917, PubMed:29319884). Recombinant protein binds to IgE in 26% of the 117 patients tested living in urban area in Austria allergic to European HDM (PubMed:18445190). Recombinant protein binds to IgE in 25% of the 96 patients tested living in Bangkok allergic to European HDM (PubMed:24874917). No relevant cross-reactivity with Der p 5 allergen (PubMed:18445190, PubMed:29319884). No relevant cross-reactivity with Blot t 5 or Lep d 5 allergens. Causes histamine release from human peripheral blood mononuclear leukocytes. Up-regulates expression of CD203c activation marker on basophils. Induces degranulation of humanized rat basophil leukemia (RBL) cells and the release of beta-hexosaminidase from them (PubMed:18445190). Triggers interleukin-8 production in human airway epithelial cells through Toll-like receptor 2 (TLR2)-dependent signaling (PubMed:24874917). The Pichia pastoris-produced protein seems to be well suited for in vitro immune cell activation assays and for in vivo applications such as immunotherapy and skin-prick testing, because it is properly folded, free of endotoxins and has the appropriate allergenic characteristics (PubMed:24874917). Non-allergenic peptides identified from the mapped major conformational IgE epitope-containing areas could be used for the engineering of house dust mite allergy vaccine (PubMed:29319884). Belongs to the mite group 5 allergen family.