ANALYSIS OF INDUCED SPUTUM FOR STUDYING ALLERGEN-SPECIFIC IGE ANTIBODIES IN AIRWAY SECRETION FROM ASTHMATIC-PATIENTS

Background Allergen-specific IgE antibodies have been considered to pl ay an important role in the pathogenesis of atopic asthma. However, st udies on allergen-specific IgE antibodies in airway secretion from ast hmatic patients are very rare compared with those in serum. Objectives The present study was undertaken to determine whether induced sputum might provide a useful method for analysing allergen-specific IgE anti bodies in airway secretions from asthmatic patients. Methods Specific IgE antibodies to house dust mite (HDM) antigen were measured in induc ed sputum from 10 HDM-sensitive asthmatic patients and 12 non-allergic controls by enzyme-linked immunosorbent assay. HDM-specific IgE was r egarded as positive when the absorbance value was higher than mean + 2 SD of controls. Their antigen-binding characteristics were determined by immunoblot analysis. Results HDM-specific IgE was positive in indu ced sputum from seven of 10 HDM-sensitive asthmatics. The IgE binding to HDM antigen could be inhibited by fluid phase HDM antigen in a dose -dependent manner, not by mugwort antigen. Treatment of induced sputum with dithiothreitol decreased the antigen-specific bindings, and incr eased the nonspecific bindings on the measurement of HDM-specific IgE. These effects were significant in a concentration of dithiothreitol g reater than 0.05%. Immunoblot analysis revealed that HDM-specific IgE antibodies in induced sputum recognized the HDM antigens with molecula r weights of 42, 34, 32, 25 and 14 kDa. These antigen binding characte ristics were similar to those in serum. Conclusion we conclude that an alysis of induced sputum is a useful non-invasive method for studying allergen-specific IgE antibodies in airway secretion from asthmatic pa tients.