NOTTINGHAM, UK—Although persons with idiopathic rhinitis (IR) have symptoms of nasal allergy, they are usually considered nonallergic because they do not have positive markers of systemic atopy, such as allergen-specific skin sensitivity and raised serum immunoglobulin E (IgE) titers. A new study has found that a proportion of these patients actually do experience characteristic TH2 hypersensitivity—the reaction, however, is localized to the nasal mucosa and independent of any systemic response.[1] The researchers coined the term entopy, meaning local resident, to describe the phenomenon.

Des G. Powe, BSc, from the School of Molecular Medical Sciences at Nottingham University and one of the study’s principal investigators, said that clinicians often see patients manifesting this form of allergy and that entopy is becoming increasingly recognized in the literature.

“We believe there to be convincing evidence supporting the concept of tissue compartmentalization [with regard to host responses],” Mr. Powe said, adding that in IR patients, all of the components necessary for an allergic inflammatory response are present in nasal mucosa, including proinflammatory cells. He said that entopy also likely exists in other allergic inflammatory conditions, including food allergy and atopic dermatitis.

EVIDENCE FOR GRASS POLLEN ALLERGY

The researchers used histochemical analysis to detect IgE antibodies specific to house dust mites and grass pollen. They examined the nasal mucosal sections of 10 nonatopic subjects with persistent rhinitis (the IR group), 11 atopic subjects with persistent rhinitis, and 12 nonrhinitic controls. The tissue turbinate samples were removed from all patients during surgery for nasal obstruction or septal deviation.

Cells from seven of the 11 subjects with allergic rhinitis stained positive for grass allergen, and cells from six stained positive for house dust mite. Cells from three of the 10 patients with IR also stained positive for grass pollen. None of the negative control samples stained for either allergen.

Based on these results and previous work his group has conducted, Mr. Powe estimated that about 13% of all patients who are currently classified as having nonallergic rhinitis actually have entopy and another 29% may have occult allergy. In other words, he said, “greater than one third of all rhinitis subjects are currently being incorrectly assigned a nonallergic status.”

One way to address this diagnostic oversight is to perform “a comprehensive review of allergens commonly used for skin sensitivity testing, as it has been proposed that [many] common allergenic factors found in the home are not routinely tested for,” Mr. Powe said. “The findings of such a study would provide us with the ability to restructure allergen panels and, as a corollary, to reduce the incidence of occult allergy.” He added that the best approach might be to use the revised allergen panel for nasal allergen challenge rather than skin testing, since the former has recently been proposed to be more effective.

WHERE THE ALLERGENS WERE FOUND

For both house dust mite allergen and grass pollen allergen, the staining was observed mostly within large mononuclear cells residing in the upper layer of the nasal submucosa. Epithelial staining was less common. Allergen was colocalized to mast cells in up to 20% of the samples from the allergic patients and 10% of the samples from the IR patients. Only 3% of the plasma cells and a negligible number of B cells had captured allergen.

Is atopy to become a dated term? “Although previously the terms atopy and allergy have been used synonymously, there is little understanding about the relationship between the presence of atopy and clinical manifestations of allergic disease,” a fact this study and many others support, Mr. Powe commented. “It is our belief that the term atopy will in time follow the same course as hay fever and be relegated to texts of historical interest only.”

—Verna L. Schwartz, MS