Expression of apoptosis-related antigen on eosinophils in chronic eosinophilic pneumonia

We examined the expression of apoptosis-related antigens Fas and bcl-2 on eosinophils from peripheral blood (PB) and bronchoalveolar lavage (BAL) in patients with chronic eosinophilic pneumonia (CEP). The expression of those antigens was assessed before and after culture with or without eosinophil chemotactic factors derived from an established T-cell line (STO-2-derived ECFs; ECF-PI5, 6, 7, 8, and 9), granulocyte-macrophage colony stimulating factor, and interleukin 5 (IL-5). We found that the expression of these antigens on eosinophils from PB increased after 24 h culture without any stimulation. In contrast, little or no change was observed even after 24 h culture in eosinophils from BAL. All STO2-derived ECFs and IL-5 suppressed Fas expression on eosinophils from PB. Furthermore, we found that eosinophils which were attracted by ECF-PI9 expressed Fas and bcl-2 more highly than those attracted by other ECFs and IL-5. Such a heterogeneous response of eosinophils to respective ECFs suggests the possibility of a heterogeneous population of eosinophils in patients with CEP.