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Lung Pharmacology Group, Dept of Respiratory Medicine and Allergology, Institute of Heart and Lung Diseases, University of Göteborg, Sahlgrenska University Hospital, Göteborg, Sweden
CORRESPONDENCE: J. Lötvall, Dept of Respiratory Medicine and Allergology, University of Göteborg, Bruna Stråket 11, 413 45, Göteborg, Sweden. Fax: 46 31413290
Keywords: allergen, asthma, eosinophils, tolerance
Received: January 17, 2000
Accepted January 7, 2001
This work was supported financially bythe Vårdal Foundation and the Swedish Heart and Lung Foundation. M. Palmqvist and J. Lötvall were financed by Herman Krefting's Foundation against Asthma-Allergy.
Allergic asthmatic individuals are often exposed to low-doses of allergen in their everyday life. Extended exposure to allergen has lead to down-regulation of the allergic process in cell systems and in animal models. The aim of this study was to evaluate whether any such inhibitory mechanism of allergic responses can be seen in man in vivo.
Patients with mild asthma were repeatedly and double-blindly exposed to 25% of the individual dose of allergen that caused an early (EAR) and late asthmatic reaction (LAR). One day after the low-dose allergen or placebo exposure periods, the same individual was given a high-dose allergen challenge. Sputum and blood were collected for the evaluation of eosinophils.
Exposure to repeated low doses of allergen induced increased bronchial methacholine responsiveness 6 h after the final allergen exposure (p=0.018), and an increase in the number of eosinophils in sputum. By contrast, the late asthmatic response after challenge with a high dose of allergen was significantly attenuated by
In summary, repeated low doses of allergen given directly to the airways, attenuate the high-dose allergen-induced late response, despite enhanced bronchial hyperresponsiveness to methacholine and elevated sputum eosinophils prior to allergen challenge.
30% at 24 h after the final low-dose allergen exposure (p=0.03).
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