Evidence for systemic rather than pulmonary effects ofinterleukin-5 administration in asthma

摘要

BACKGROUND—Interleukin 5 (IL-5) has an important role in mobilisation of eosinophils from the bone marrow and in their subsequent terminal differentiation. A study was undertaken to determine whether inhaled and intravenous IL-5 could induce pulmonary eosinophilia and bronchial hyperresponsiveness (BHR) independently of these effects.
METHODS—Nine mild asthmatics received inhaled (15 µg) or intravenous (2 µg) IL-5 or placebo in random order in a double blind, crossover study. Blood samples were taken before and at 0.5, 1, 2, 3, 4,5, 24, and 72 hours following IL-5 or placebo, and bronchial responsiveness (PC20 methacholine) and eosinophil counts in induced sputum were determined.
RESULTS—Serum IL-5 levels were markedly increased 30 minutes after intravenous IL-5 (p=0.002), and sputum IL-5 levels increased 4and 24 hours after inhaled IL-5 (p<0.05). Serum eotaxin was raised 24 hours after intravenous IL-5 but not after inhaled IL-5 or placebo. Blood eosinophils were markedly reduced 0.5-2 hours after intravenous IL-5 (p<0.05), followed by an increase at 3, 4, 5,and 72 hours (p<0.05).Sputum eosinophils rose significantly in all three groups at 24 hoursbut there were no differences between the groups. Bronchialresponsiveness was not affected by IL-5.
CONCLUSION—The effectsof IL-5 appear to be mainly in the circulation, inducing peripheralmobilisation of eosinophils to the circulation without any effect oneosinophil mobilisation in the lungs or on bronchial responsiveness.