Evidence for interleukin-5 in nasal polyps in aspirin-induced asthma

Aspirin-induced asthma is often accompanied by nasal polyps, in which tissue eosinophils are abundant and activated. However, the mechanism of eosinophil infiltration remains unknown. We encountered two aspirin-induced asthma patients with nasal polyps and investigated eosinophil infiltration into nasal polyp tissue. Eosinophil chemotactic activity of extracts from the nasal polyp was elevated and could be inhibited by 40% with anti-interleukin (IL)-5 antibody. Interleukin-5 was detectable in the extract. The chemotactic activity of peripheral blood eosinophils to recombinant human (rh) IL-5 was increased compared with normal volunteers. Messenger RNA expression for IL-5 in CD3+ lymphocytes for polyp tissue was detected using the reverse transcription-polymerase chain reaction. These results suggest that IL-5 from local T lymphocytes may be one of the candidates for recruitment of eosinophils into nasal polyps in aspirininduced asthma.