Inhaled IL-5 increases concentrations of soluble intracellular adhesion molecule-1 in sputum from atopic asthmatic...

Both IL-5 and intracellular adhesion molecule-1 (ICAM-1) have been shown to play important roles in the production of allergic inflammation, including atopic asthma.

The aim of this study was to investigate the effects of recombinant human IL-5 on changes of soluble (s) ICAM-1 concentrations in induced sputum from allergic asthmatic subjects.

In a randomized, double-blind, placebo-controlled study design, 8 nonsmoking patients with allergic asthma and 6 nonallergic normal subjects were administered recombinant human IL-5 by nebulization, and the concentrations of sICAM-1 in induced sputum from each subject were determined before and at 2, 24, 48, and 72 hours after inhalation.

sICAM-1 levels in sputum within the control group did not appear to change from baseline at any time throughout the study. In allergic asthmatic subjects vehicle challenge was not able to cause any changes in sputum sICAM-1 concentrations. However, there were increases in sputum sICAM-1 concentrations after IL-5 inhalation, which increased with time to significantly greater levels than those at baseline, reaching a maximum at 48 hours and lasting no less than 72 hours. The concentrations of sICAM-1 in sputum after IL-5 challenge exceeded levels that could be accounted for by passive transudation from the circulation on the basis of the magnitude of increases in sputum albumin concentration.

Our results indicated that IL-5 inhalation was capable of inducing an elevation of sputum sICAM-1 concentration by stimulating its local release in allergic asthmatic, but not in nonallergic normal, subjects.