IL-5 ACCOUNTS FOR THE MOUSE PLEURAL EOSINOPHIL ACCUMULATION TRIGGEREDBY ANTIGEN BUT NOT BY LPS

The involvement of interleukin-5 (IL-5) in the pleural eosinophilia in duced by LPS or allergen was investigated. The number of pleural eosin ophils in actively sensitized mice increased 24 h after the intrathora cic (i.t.) injection of ovalbumin (12 mg/cavity), peaked within 72 h, and persisted significantly increased for at least 120 h. Despite bein g less intense, the i.t. injection of LPS (250 ng/cavity) also increas ed the number of pleural eosinophils at 24 h, returning to basal level s within 72 h. Intraperitoneal pretreatment with monoclonal antibody t o IL-5 (TRFK-4 and TRFK-5, 500 mg/kg) suppressed the eosinophil accumu lation induced by IL-5 (200 units/cavity) or ovalbumin, but had no eff ect on the LPS-induced eosinophilia. Transfer of the cell-free pleural washing from LPS-treated donor mice to naive recipient animals led to a selective increase in the eosinophil counts. The co-incubation of t he pleural washing from LPS-treated animals with monoclonal antibody t o IL-5 failed to modify the phenomenon. The results indicate that IL-5 plays an important role in the antigen-induced accumulation of eosino phils in vivo, but not in the eosinophilia triggered by LPS.