In tracheal aspirates from preterm infants mechanically-ventilated for respiratory distress in the first week of life levels of FLT3L, IL-12p40, IL-12p70 and IFN-γ were higher in infants who went on to develop BPD and FLT3L levels positively correlated with proinflammatory cytokines levels. This evidence concerns the gene FLT3LG and bronchopulmonary dysplasia.