Characterization of airway inflammation after repeated exposures to occupational agents

Background: Little is known about the comparative kinetics of eosinophil re cruitment after exposure to low- and high-molecular-weight sensitizers in s ubjects with occupational asthma (OA). Objectives: The aims of the study were to investigate the kinetics of chang es in inflammatory mediators associated with eosinophil infiltration (IL-5 and eotaxin) and to examine the nature of the airway inflammation induced i n response to different types of occupational agents. Methods: We investigated 15 subjects with OA caused by high- and low-molecu lar-weight agents. The subjects were exposed to increasing doses of the rel evant 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 co unts, 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 eosi nophils was more prominent in subjects exposed to low-molecular-weight agen ts than to high-molecular-weight agents. Conclusion: Changes in eosinophils, IL-5, and eotaxin precede functional ch anges after exposure to occupational agents in subjects with OA, Eosinophil inflammation is a feature of exposure to both high- and low-molecular-weig ht agents. Induced sputum may be a useful tool in the early diagnosis of OA .