Rhinitis with negative skin tests and absent serum allergen-specific IgE: More evidence for local IgE?

The phenomenon of local production of IgE in the nasal mucosa is well documented in subjects with allergic rhinitis who have raised serum specific IgE and positive skin prick tests to clinically relevant allergens.1, 2, 3, 4 Local IgE has also been detected in high levels in nasal polyps in which Staphylococcus-derived enterotoxins are associated with elevated enterotoxin-specific IgE antibodies and likely act as superantigens, thereby promoting increases in polyclonal IgE.5 Nonallergic rhinitis in the absence of systemic allergen-specific IgE with/without associated eosinophilia affects approximately 25% of patients who experience symptoms of rhinitis.6 In a subset of this group of heterogeneous disorders, IgE is detectable within the nasal mucosa and/or nasal secretions, implying that an IgE-mediated allergic response may be localized exclusively to the target organ. Huggins and Brostoff7 originally demonstrated the presence of specific IgE in nasal secretions of patients with rhinitis with negative skin prick tests. A number of studies since have provided further evidence of local allergic rhinitis in such patients.8, 9, 10, 11

Rondón et al12 previously reported elevations in allergen-specific IgE in nasal lavage in a proportion of subjects who responded positively to a nasal allergen challenge in the absence of positive skin tests or elevated allergen-specific IgE. In this issue of the Journal,13 Rondón et al describe the associated local inflammatory response in 30 such patients. The mean age of onset of local allergic rhinitis in the cohort was 31 years, with a female to male bias of 19:11. Nearly half (14/30) of the patients with local allergic rhinitis had asthma, and 57% (17/30) had conjunctivitis. Symptoms were assessed by using a visual analogue scale and nasal patency by acoustic rhinometry at intervals after nasal provocation with grass pollen extract. Tryptase, eosinophilic cationic protein, and grass pollen–specific IgE were measured in nasal lavage. Intranasal challenge resulted in immediate (15 minutes to 1 hour) responses in all subjects and additional late responses (6-24 hours) in 70% of those tested. The proportion of patients with an isolated immediate response was similar to previous studies by the authors.10, 12 Although the significance of an absent late response is questionable, 90% of patients with isolated immediate responses had conjunctivitis compared with 57% in those with dual responses.

Tryptase in nasal lavage, a marker of mast cell activation, was increased in 40% of subjects. Levels peaked at 15 minutes and remained elevated for 24 hours. Increased mast cell numbers have previously been identified in the nasal mucosa of patients with nonallergic rhinitis compared with healthy controls.14, 15 There was a correlation between tryptase and immediate nasal symptoms of itching and sneezing. Eosinophilic cationic protein, a marker of eosinophil activation, was detected at 15 minutes and continued to rise over a period of 24 hours in 43% of subjects. Eosinophilic cationic protein correlated only with nasal obstruction, which was more frequently reported during late responses. Time-dependent increases in grass pollen–specific IgE up to 24 hours were detected in nasal lavage in 9 of 30 subjects, in 4 of whom specific IgE was detectable before challenge despite the study being conducted outside the pollen season. These and previous data3, 10, 12 imply that the absence of systemic IgE does not necessarily exclude local IgE-mediated allergic disease.

There are some limitations to the findings. Local specific IgE was not detected in the majority of positive responders to grass pollen. The specificity of the local IgE response could have been further examined by including, in addition to healthy controls, a control group of patients with rhinitis with negative responses to nasal grass pollen challenge. The authors argue that the detection of local IgE in only a proportion may be secondary to a dilution effect of the nasal lavage procedure, whereas their findings are consistent with previous studies. Powe et al8 identified positive immunostaining for grass pollen–specific IgE within the nasal mucosa in 30% (3/10) of patients with idiopathic rhinitis. Rondón et al12 previously identified specific IgE in nasal lavage in only 22% (7/32) of those subjects with idiopathic rhinitis who responded to grass pollen challenge. It remains to be determined what causes inflammation in the remaining 70%. One possibility is that grass pollen–associated proteins or lipid mediators activate eosinophils and/or other inflammatory cells directly and independently of IgE as previously shown for tree pollen.16

What are the clinical implications? First, it is well known that some atopic individuals develop rhinitis whereas others develop asthma and/or atopic dermatitis, and some subjects have no clinical manifestations despite positive skin tests and/or specific IgE. The local provenance of IgE at mucosal sites might explain this discrepancy. Second, as shown by Rondón et al12 and in previous studies of intrinsic rhinitis17 and asthma,18, 19 local IgE could explain the occurrence of disease in the absence of systemic allergen-specific IgE. The implication is that nasal and/or bronchial allergen provocation might have a more prominent role in diagnosis when the clinical history is highly suggestive of involvement of an environmental allergen despite negative skin tests and serum allergen-specific IgE. Third, despite confirmation of local IgE protein production,12, 20 it is not clear to what extent local versus systemically produced IgE contributes to disease burden. Local strategies directed against IgE might resolve this issue and potentially provide a novel treatment approach. A pilot study of local inhaled anti-IgE in atopic asthma21 was associated with the occurrence of sensitization against the mAb when used via the mucosal route. The development of small molecule inhibitors for topical use directed against either IgE interaction with its receptors22 or the mechanism of switching of B cells in favor of IgE might be effective and might circumvent this problem.