Difference in apoptotic function between eosinophils from peripheral blood and bronchoalveolar lavage in chronic eosinophilic pneumonia

We compared apoptosis in eosinophils from bronchoalveolar ravage (BAL-Eos) with that in eosinophils from peripheral blood (PB-Eos) of 4 patients with chronic eosinophilic pneumonia (CEP). The survival rate of the BAL-Eos on the 3rd day of the culture was significantly higher than that of the PB-Eos (39.1 vs. 1.3%). The percentage of apoptotic cells in the PB-Eos after a 24-hour incubation was higher than that in the BAL-Eos (21.7 vs. 10.6%) according to an analysis with annexin V. We further found that ECF-PI9, an eosinophil chemotactic factor (ECF) derived from an established T cell line (STO-2), significantly suppressed the apoptosis of both PB-Eos and BAL-Eos and prolonged their survival. The expression of Fas on PB-Eos was significantly suppressed by ECF-PI9 (18.5 to 7.37%, p < 0.05), whereas ECF-PI9 failed to suppress the Fas expression on BAL-Eos (3.3 to 3.6%). In addition, an ECF with similar physicochemical properties and biological functions was isolated from the BAL fluid of patients with CEP. These data demonstrate differences between PB-Eos and BAL-Eos, and indicate that ECF-PI9 is involved in the pathogenesis of CEP.