Influence of Natural Exposure to Pollens and Domestic Animals on Airway Responsiveness and Inflammation in Sensitized Non-Asthmatic Subjects

Abstract

Background: Atopy may be a risk factor in the development of asthma. Indoor allergens are considered to be more potent asthma inducers than outdoor ones such as pollens. Lower airway inflammation may be present in non-asthmatic subjects during natural exposure to relevant allergens and may eventually lead to the development of asthma. Aims: To document seasonal variation in lower airway responsiveness and inflammation in sensitized non-asthmatic subjects, during natural exposure to allergens, and to determine whether it is more marked in those exposed to animals to which they are sensitized. Methods: Twenty-two atopic subjects were seen during and out of the pollen season. All (but the controls) were sensitized to domestic animals, and to trees, grasses or ragweed. Eleven were not exposed to animals at home and 8 were exposed. They were compared with 3 normal controls. A respiratory questionnaire was administered, allergy skin prick tests, spirometry, methacholine challenge, blood and induced sputum with differential cell counts were obtained during the pollen season for all subjects. These tests were repeated out of the pollen season. Results: Throughout the study, none of the subjects had asthma symptoms. Mean PC₂₀ was significantly lower in subjects exposed to animals compared with unexposed subjects or controls, both during and out of the pollen season. In season, subjects exposed to animals had significantly higher sputum eosinophil numbers than unexposed or normal control subjects. Conclusions: Non-asthmatic atopic subjects show variable degrees of airway responsiveness and inflammation. However, subjects exposed to animals show higher airway eosinophilia, which may suggest they are at increased risk of developing airway hyperresponsiveness and asthma.

Rinitis y asma: una vía respiratoria, una enfermedad

“…Encontraron un aumento de los marcadores de la inflamación (proteína catiónica de los eosinófilos y molécula de adhesión intercelular) en esputo, lo cual se relacionó con un aumento de la interleucina 5 en el plasma. Otros trabajos han demostrado una respuesta inflamatoria bronquial en pacientes con rinitis alérgica sin asma tras la exposición natural a pólenes y tras provocaciones repetidas a dosis bajas [29][30][31][32] .…”

Allergen‐induced early and late asthmatic responses to inhaled seasonal and perennial allergens

“…We previously showed that domestic allergens such as HDM and animal danders could induce more marked airway eosinophilia than seasonal allergens, even in atopic non‐asthmatic subjects, a factor that could possibly enhance changes in airway function following exposure to such allergens .…”

The allergen bronchoprovocation model: an important tool for the investigation of new asthma anti‐inflammatory therapies

“…Indeed, up to 30% of patients with chronic allergic rhinitis have asthma and rhinitic patients often show AHR (16). Lower airway inflammation has been demonstrated in rhinitic subjects without any evidence of asthma or AHR (17)(18)(19). In asthmatic subjects, the nasal inflammatory process shares many similarities with that of lower airways (20).…”