Environmental and occupational disorders
Characterization of airway inflammation after repeated exposures to occupational agents,☆☆

https://doi.org/10.1067/mai.2000.111235Get rights and content

Abstract

Background: Little is known about the comparative kinetics of eosinophil recruitment after exposure to low- and high-molecular-weight sensitizers in subjects with occupational asthma (OA). Objectives: The aims of the study were to investigate the kinetics of changes in inflammatory mediators associated with eosinophil infiltration (IL-5 and eotaxin) and to examine the nature of the airway inflammation induced in response to different types of occupational agents. Methods: We investigated 15 subjects with OA caused by high- and low-molecular-weight agents. The subjects were exposed to increasing doses of the relevant occupational agent over 3 to 4 days until a 20% fall in FEV1 occurred. Methacholine challenge and sputum induction were performed at the end of each day of exposure. Sputum samples were assessed for differential cell counts, including eosinophils, IL-5, and eotaxin messenger RNA. Results: There was an increase in sputum eosinophils, eotaxin, and IL-5 on the day preceding the occurrence of asthmatic reaction, although there was no change in functional parameters (FEV1 and PC20). Increase in sputum eosinophils was more prominent in subjects exposed to low-molecular-weight agents than to high-molecular-weight agents. Conclusion: Changes in eosinophils, IL-5, and eotaxin precede functional changes after exposure to occupational agents in subjects with OA. Eosinophil inflammation is a feature of exposure to both high- and low-molecular-weight agents. Induced sputum may be a useful tool in the early diagnosis of OA. (J Allergy Clin Immunol 2000;106:1163-70.)

Section snippets

Study design

We recruited subjects with OA previously diagnosed by using specific inhalation challenges (SICs) in whom the dose of occupational agent necessary to induce an asthmatic reaction was determined. On the first day (control day), they were given a questionnaire regarding their respiratory symptoms, smoking habits, and current treatment for asthma. On day 2, subjects were exposed to half the dose of occupational agent that induced an asthmatic reaction at the time of the diagnosis. On day 3,

Results

Twenty-seven subjects were enrolled, but 12 were excluded because they experienced an asthmatic reaction the first day of exposure (n = 6), did not experience any reaction (n = 3), or did not wish to continue their participation (n = 3). The study protocol was completed in 15 subjects. The clinical characteristics of these subjects are listed in Table I.

. Clinical characteristics of the subjects

Patient No.SexAge (y)Smoking* (duration of cessation)AtopyAgentDuration of exposure (y)Time between

Discussion

We observed an increase in inflammatory indices associated with eosinophilic infiltration (sputum eosinophils, IL-5, and eotaxin mRNA+ cells) that preceded any significant change in functional parameters (FEV1 and PC20) in subjects with OA after exposure to occupational sensitizers. These findings are consistent with observations previously made in patients with asthma in whom an increase in sputum eosinophils precedes the occurrence of asthma exacerbations25, 26 and in whom a low dose of

Acknowledgements

We thank Drs André Cartier and Jean-Luc Malo for reviewing the article.

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  • Cited by (0)

    Supported by Institut de Recherche en Santé et Sécurité au Travail (IRSST). C. Lemière and Q. Hamid are scholars of the Fonds de la recherche en santé du Québec.

    ☆☆

    Reprint requests: Catherine Lemière, MD, Department of Chest Medicine, Sacré-Coeur Hospital, 5400 West Gouin, Montreal, Quebec, Canada, H4J 1C5.

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