Der p23, a dangerous new allergen from house dust mites (HDM)

Chambered gut of the house dust mite

1. Food held. 2. Der p23 is dropped from cells. 3. Hindgut with wrapped dropping

Within the film Der p23 appears as a peritrophin-like protein that acts to bind together matter such as chitin fibrils and granules. The film itself is a semi-permeable network of fibres that dissolve on contact with moisture.

In terms of allergen importance it ranks alongside Der p1 and Der p2 with over 70% of house dust mite allergy patients allergic to Der p23. The allergen is reported to be an active digestive enzyme.(3)

The newly discovered Der p23 is one more reason to avoid excessive exposure to house dust mites, a mite recently described as a close relative of the parasitic mange mite, P ovis.(4,5,6)

For further research information on the film that covers a house dust mite dropping, please refer to the 1972 paper quoted below.(2)

The membrane surrounding the food balls in the posterior midgut is 1 to 2 microns thick. The inner and outer margins of the membrane appear more electron-dense than the central region. The electron-dense inner margin of the membrane contains numerous granules. The outer wall of the membrane is composed largely of a mat of extremely fine fibrils (approximately 3.5 by 300 nm). The central portion of the membrane contain fewer granules and fibers. In the hindgut, the membrane remains intact and there surrounds a fecal particle. The three to five fecal particles that form a fecal pellet are held together by what appears to be mucus.

Notes: Chitinases, an enzyme that digests chitin, is a known allergen from house dust mites. Chitin forms the outer wall of fungi and was in 1972 thought to be part of the peritrophic membrane encasing the mite's dropping. Fungi are an important food for the mite. Records show that the house dust mite is a 23 million year old animal that survived the dinosaurs.