Strikingly, BAL fluid-to-serum ratios of most of the measured biomarkers yielded values close to 1 in ARDS and controls, indicating no concentration gradient between the alveolar and blood compartments, while values greater than one were observed for SP-D, IL-6, IL-8 and IP-10/CXCL10. This evidence concerns the gene CXCL8 and acute respiratory distress syndrome.