CELL INFILTRATION, ICAM-1 EXPRESSION, AND EOSINOPHIL CHEMOTACTIC ACTIVITY IN ASTHMATIC SPUTUM

We have applied the technique of sputum induction by hypertonic saline in asthmatics and nonatopic control subjects to study an array of ind ices of airway inflammation believed to be relevant to asthma pathogen esis. Compatible with a central role for eosinophils and mast cells in asthma, sputum of asthmatic subjects contained increased numbers of e osinophils and levels of eosinophil cationic protein (ECP) and mast ce ll tryptase. Eosinophil numbers, and ECP and histamine levels correlat ed with the degree of methacholine airways responsiveness, and ECP, tr yptase, and histamine correlated with raised concentrations of albumin . Using the micro-Boyden chamber technique eosinophil chemotactic acti vity was identified only in the sputum from asthmatics. The correlatio n between the raised levels of total IgA, IL-8/IgA complexes, and tryp tase and the degree of sputum eosinophilia and ECP levels, suggests po ssible mechanisms for eosinophil chemotaxis and activation in asthma, Flow cytometric analysis of sputum lymphocytes showed an increase in C D4(+) T cells and T cells expressing intercellular adhesion molecule-1 (ICAM-1) in asthma which, together with the finding of raised levels of soluble ICAM-1 in the sputum, indicates upregulation of this adhesi on molecule. Finally, the proportion of CD16(+) natural killer (NK) ce lls was reduced in the sputum of asthmatics. These observations highli ght the importance of the airway inflammation In causing asthma and fu rther confirm the usefulness of sputum induction as a tool in asthma r esearch.