Increased interleukin-5 levels in bronchoalveolar lavage fluid is a major factor for eosinophil accumulation in acute eosinophilic pneumonia

Background. Increased interleukin-5 (IL-5) levels have been reported in bro nchoalveolar lavage fluid (BALF) from patients with acute eosinophilic pneu monia (AEP); however, it still remains to be determined whether IL-5 is res ponsible for the eosinophil accumulation in the lung. Objective: We examine d the effect of antibodies against cytokines on eosinophil chemotaxis induc ed by BALF from AEP patients to identify factors responsible for eosinophil accumulation. Methods: We measured a series of specific cytokines, includi ng IL-3, IL-4, IL-5, IL-6, IL-8, GM-CSF, RANTES, MCP-1, MIP-1 alpha and eot axin, in the BALF from 4 patients with AEP. BALF from 4 patients with chron ic eosinophilic pneumonia (CEP) and 13 patients with non-eosinophilic inter stitial lung diseases OLD) were examined as controls. The eosinophil chemot actic activity in the BALF was examined using tissue culture insert furnish ed with a polycarbonate membrane. Results: The total protein content in BAL F from patients with AEP was extremely elevated. Even after standardization with protein concentration, IL-5 levels in AEP patients were significantly higher than those in CEP and ILD. IL-3 and chemokines were rather lower in the AEP group than in the CEP and ILD groups. In AEP BALF, anti-IL-5 neutr alizing antibody significantly inhibited eosinophil chemotaxis. Antibodies against IL-3, GM-CSF, and IL-8 did not affect the eosinophil migration. Con clusion: These findings suggest that locally produced IL-5 plays an importa nt role in eosinophil accumulation of AEP. Copyright (C) 2001 S. Karger AG, Basel.