Neonatal respiratory failure in mice lacking lymphatics results from failure of lung inflation. (A) Exposure of Ccbe1^−/− and littermate control neonates to 100% oxygen (O₂) for 30 min. Bars, 5 mm. Images are representative of 4 control and 3 Ccbe1^−/− neonates from 1 litter. (B and C) Flotation of cyanotic Ccbe1^−/− and Vegfr3^kd/kd neonate lungs in saline compared with control littermates and non-cyanotic Ccbe1^−/− or Vegfr3^kd/kd neonatal lungs. Bars, 5 mm. Images are representative of 24 control and 9 lymphatic-deficient neonates examined from 5 independent experiments. (D) H-E–stained sections of lung from cyanotic and non-cyanotic neonates. Bars, 200 µm. Representative images are shown from 6 control, 5 cyanotic, and 3 non-cyanotic Vegfr3^kd/kd neonates examined from 4 independent litters in each group.