Evidence for systemic rather than pulmonary effects of interleukin-5 administration in asthma.
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 microg) or intravenous (2 microg) 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 (PC(20) 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 4 and 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 hours but there were no differences between the groups. Bronchial responsiveness was not affected by IL-5.


CONCLUSIONS
The effects of IL-5 appear to be mainly in the circulation, inducing peripheral mobilisation of eosinophils to the circulation without any effect on eosinophil mobilisation in the lungs or on bronchial responsiveness.
van Rensen
E L
EL
Department of Thoracic Medicine, National Heart and Lung Institute, Imperial College School of Medicine, London SW3 6LY, UK.
Stirling
R G
RG
Scheerens
J
J
Staples
K
K
Sterk
P J
PJ
Barnes
P J
PJ
Chung
K F
KF
D000280:Administration, Inhalation; D000328:Adult; D000704:Analysis of Variance; D001249:Asthma / Q000188:drug therapy* / Q000378:metabolism; D001985:Bronchial Provocation Tests; D002452:Cell Count; D054413:Chemokine CCL11; D019742:Chemokines, CC / Q000097:blood; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007262:Infusions, Intravenous; D015848:Interleukin-5 / Q000008:administration & dosage / Q000032:analysis / Q000494:pharmacology*; D008297:Male; D011657:Pulmonary Eosinophilia / Q000139:chemically induced; D013183:Sputum / Q000166:cytology
C515456:CCL11 protein, human; D054413:Chemokine CCL11; D019742:Chemokines, CC; D015848:Interleukin-5